Detection circuit for alternating current entering direct current
By using capacitive components and optocoupler devices in the DC system for electrical isolation and converting analog signals into level signals, the problems of high cost and inaccurate detection of existing equipment are solved, and a simple structure and low cost AC into DC detection circuit is realized, which is suitable for civil application scenarios.
Patent Information
- Application Number
- CN202420986229.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-09
- Publication Date
- 2025-04-18
- Estimated Expiration
- 2034-05-09
AI Technical Summary
The existing DC system detects the equipment that intercepts AC power, such as high cost, large volume and high energy consumption, limiting its application in the civilian field.
Capacitor components and optocoupler devices are used for electrical isolation, the analog signal is converted into level signals through the optocoupler signal change circuit, and the signal is processed using an ordinary digital microcontroller to determine whether AC power is flew into the DC system.
Reduces system costs, improves system safety, simplifies circuit design, and improves resistance to noise and disturbances, enhancing detection accuracy.
Smart Images
Figure CN222774621U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of electronic technology, in particular to an AC-DC detection circuit. Background Art
[0002] DC power supply technology plays an increasingly important role in modern power systems, especially in the fields of renewable energy, electric vehicle charging stations and data centers. In a DC system, if AC is accidentally introduced, it will affect the stable operation of the entire DC system, or may damage sensitive electronic equipment in the DC system, or even cause safety accidents such as fire. Monitoring whether AC is mixed into the DC system can improve the reliability of the entire DC system, reduce unexpected downtime and maintenance time caused by AC intrusion, and protect the safety of personnel and equipment.
[0003] Currently, most of the devices used to detect AC intrusion in DC systems are aimed at industrial applications. They generally include the following four circuits:
[0004] Isolation devices: used to achieve electrical isolation to ensure safety. In industrial applications, this usually involves high voltage and high current, so the cost is high.
[0005] Analog signal conditioning circuit: converts AC signals into a format suitable for ADC sampling, usually including functions such as filtering, amplification and buffering, and its circuit design is relatively complex.
[0006] Analog signal to digital signal (ADC) circuit: converts analog signal into digital signal.
[0007] Microcontroller (MCU module): Draws a voltage curve based on the collected voltage digital signal to determine whether AC power is connected to the DC bus;
[0008] Therefore, the existing equipment for detecting AC intrusion in DC systems has problems such as high cost, large size, and high energy consumption, which limits their application in the civilian field. Utility Model Content
[0009] The utility model aims to solve the above problems and provide an AC-DC current leakage detection circuit which has a simple structure and can reduce costs.
[0010] The beneficial contribution of the utility model is that it effectively solves the above problems. The utility model uses a capacitor element to isolate the AC component in the DC system, thereby realizing the detection of AC signals; in addition, the utility model provides electrical isolation through an optocoupler device, and converts the analog signal into a level signal at the same time, which not only realizes the signal conversion, but also increases the safety of the system due to the isolation characteristics of the optocoupler; in addition, the utility model uses a low-cost ordinary digital single-chip microcomputer to process the signal. The single-chip microcomputer reads the level signal output by the optocoupler and analyzes the frequency of its high and low changes, thereby determining whether there is an AC power supply connected to the DC bus, avoiding the use of a high-precision analog sampling (ADC) solution, thereby reducing the system cost.
[0011] Compared with the prior art, the utility model has the following advantages:
[0012] 1. By using common digital microcontrollers and optocouplers, the need for high-precision analog sampling equipment is reduced, thereby reducing overall costs;
[0013] 2. The isolation characteristics of the optocoupler can greatly improve the safety of the system;
[0014] 3. Avoids complex analog signal conditioning and analog-to-digital conversion processes, simplifying circuit design;
[0015] 4. By setting thresholds and frequency analysis, the system's resistance to noise and disturbance is improved, and the accuracy of detection is improved.
[0016] The civil AC-DC leakage detection circuit of the utility model has the characteristics of simple structure and low cost, and is highly practical. It is particularly suitable for civil application scenarios and can be widely used in household DC power supply projects. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 It is a schematic diagram of the circuit structure of the present invention.
[0018] Figure 2 is a circuit diagram of another embodiment.
[0019] Figure 3 is a circuit diagram of another embodiment.
[0020] Figure 4 It is a simulation circuit diagram.
[0021] Figure 5 yes Figure 4 The simulation results are shown in Figure 2.
[0022] Figure 6 This is another simulation circuit diagram.
[0023] Figure 7 yes Figure 6 The simulation structure. DETAILED DESCRIPTION
[0024] The following embodiments are provided to further explain and supplement the present invention and do not constitute any limitation to the present invention.
[0025] The utility model discloses an AC-DC current detection circuit, which comprises a DC-isolating capacitor C1, an optocoupler signal changing circuit and an MCU module.
[0026] The DC blocking capacitor C1 can block the DC voltage from passing through and allow the AC signal to pass through. It is used to isolate the DC component in the DC bus voltage, thereby forming a signal without a DC component on one side of the DC blocking capacitor C1, which helps to detect the presence of AC in the DC system. The DC blocking capacitor C1 is connected to the DC bus and is connected to the positive or negative pole of the DC bus.
[0027] The optocoupler signal change circuit is used to convert the alternating current higher than the first voltage threshold into a level signal. The optocoupler signal change circuit is provided with an optocoupler. The input end of the optocoupler is connected to the DC blocking capacitor C1 and the ground end, and it receives the AC signal and emits light through the LED. After receiving the light signal, the photosensitive receiver generates a corresponding level change and outputs it to the MCU module. The MCU module determines whether there is an AC signal intrusion according to the level signal.
[0028] Through the optocoupler signal conversion circuit, the analog signal can be cleverly converted directly into a level signal, thereby reducing the demand for high-precision analog sampling equipment and reducing overall costs; at the same time, due to the high-voltage isolation characteristics of the optocoupler, the dangerous high-voltage circuit can be directly isolated, thereby greatly improving the safety of the system.
[0029] Furthermore, the optocoupler signal change circuit includes a first current limiting resistor R1. One end of the first current limiting resistor R1 is connected to the DC blocking capacitor C1, and the other end is connected to the optocoupler. The resistance value of the first current limiting resistor R1 can be set as needed. After the AC signal passes through the DC blocking capacitor C1, the first current limiting resistor R1 can be used for voltage division and current limiting, so as to adjust the amplitude of the signal to make it suitable for subsequent optocoupler work. By selecting the first current limiting resistor R1 and the DC blocking capacitor C1 with appropriate parameters, the detected AC voltage amplitude can be adjusted, that is, the first voltage threshold is adjusted, so that only AC higher than the first voltage threshold can trigger the optocoupler to form an effective high and low level change. In this way, noise interference can be filtered out and the accuracy of detection can be improved.
[0030] Further, the optocoupler includes a first optocoupler U1. The first optocoupler U1 includes a first light-emitting diode D1 and a first phototransistor Q1. The first light-emitting diode D1 is a transmitter, and the first phototransistor Q1 is a photosensitive receiver. The positive electrode of the first light-emitting diode D1 is connected to the first current-limiting resistor R1, and the negative electrode is connected to the ground terminal. The collector of the first phototransistor Q1 is connected to the positive electrode VDD of the logic power supply, and the emitter is connected to the first port AC_N of the MCU module. When the AC voltage meets the conditions and the first light-emitting diode D1 is turned on, the first phototransistor Q1 is excited, and the output end of the first optocoupler U1 can output a high level to the first port AC_N of the MCU module, otherwise it outputs a low level. In this way, the MCU module can obtain high and low level signals, so as to facilitate the analysis of the AC signal and determine whether it is AC intrusion.
[0031] The optocoupler signal change circuit can use a single optocoupler or a dual optocoupler. When it is necessary to judge the positive and negative pulses, the optocoupler signal change circuit can use a dual optocoupler; when only a single pulse is detected, the optocoupler signal change circuit can use a single optocoupler. For example,
[0032] In some embodiments, Figure 2 As shown, the optocoupler signal change circuit can only detect the positive half-wave of the AC signal. In this case, the optocoupler can only include the first optocoupler U1. In the positive half-wave period of the AC signal, when the amplitude of the AC signal exceeds the first voltage threshold, the first light-emitting diode D1 is turned on, the first phototransistor Q1 is excited, the current flows from the collector to the emitter, and the output end of the first optocoupler U1 outputs a high level to the first port AC_N of the MCU module. When the amplitude of the AC signal is lower than the first voltage threshold or in the negative half-wave period of the AC signal, the first light-emitting diode D1 and the first phototransistor Q1 are cut off, and at this time, the output end outputs a low level to the first port AC_N of the MCU module. In this way, the MCU module can obtain high and low level signals through the first port AC_N, so as to perform subsequent analysis and calculation to determine whether there is AC intrusion.
[0033] In some embodiments, Figure 1 As shown, the optocoupler signal change circuit can detect positive and negative pulse alternating current. At this time, the optocoupler includes not only the first optocoupler U1 but also a second optocoupler U2.
[0034] like Figure 1As shown, the second optical coupler U2 includes a second light-emitting diode D2 and a second phototransistor Q2. The anode of the second light-emitting diode D2 is connected to the cathode of the first light-emitting diode D1, and the cathode of the second light-emitting diode D2 is connected to the anode of the first light-emitting diode D1. The anode of the second phototransistor Q2 is connected to the positive electrode VDD of the logic power supply, and the emitter is connected to the second port of the MCU module.
[0035] like Figure 1 As shown, in the positive half-wave cycle of the AC signal, when the amplitude of the AC signal exceeds the first voltage threshold, the first light-emitting diode D1 is turned on, the second light-emitting diode D2 is turned off, the first phototransistor Q1 is excited, and the second phototransistor Q2 is turned off. At this time, the output end of the first optocoupler U1 outputs a high level to the first port AC_N of the MCU module, and the output end of the second optocoupler U2 outputs a low level to the second port of the MCU module. When the AC signal flips to the negative half-wave cycle, and the amplitude of the AC signal exceeds the first voltage threshold, the first light-emitting diode D1 is turned off, the second light-emitting diode D2 is turned on, the first phototransistor is turned off, and the second phototransistor Q2 is turned on. At this time, the output end of the first optocoupler U1 outputs a low level to the first port AC_N of the MCU module, and the output end of the second optocoupler U2 outputs a high level to the second port of the MCU module. In this way, the MCU module can obtain high and low level signals through the first port AC_N and the second port, so as to perform subsequent analysis and calculation to determine whether there is AC intrusion.
[0036] The first port AC_N and the second port may be the same port or two independent ports. Figure 1 As shown, the first port AC_N and the second port are preferably two independent ports.
[0037] In some embodiments, Figure 3As shown, the optocoupler signal change circuit can only detect the positive half-wave of the AC. In this case, the optocoupler can only include the first optocoupler U1, and the optocoupler signal change circuit can further include a third diode D3. The anode of the third diode D3 is connected to the cathode of the first light-emitting diode D1, and the cathode of the third diode D3 is connected to the anode of the first light-emitting diode D1. In the positive half-wave period of the AC signal, when the amplitude of the AC signal exceeds the first voltage threshold, the first light-emitting diode D1 is turned on, the third diode D3 is turned off, the first phototransistor Q1 is excited, the current flows from the collector to the emitter, and the output end of the first optocoupler U1 outputs a high level to the first port AC_N of the MCU module. When the amplitude of the AC signal is lower than the first voltage threshold or in the negative half-wave period of the AC signal, the third diode D3 is turned on, the first light-emitting diode D1 and the first phototransistor Q1 are turned off, and at this time, the output end of the first optocoupler U1 outputs a low level to the first port AC_N of the MCU module. In this way, the MCU module can obtain high and low level signals through the first port AC_N, so as to perform subsequent analysis and calculation to determine whether there is AC intrusion.
[0038] Furthermore, the third diode D3 is a fast recovery diode, which has a very short reverse recovery time, can withstand a higher switching speed, and has lower heat generation.
[0039] In this way, the optocoupler signal changing circuit realizes the conversion of the alternating current of the analog signal into high and low level level signals. By adjusting the resistance value of the first current limiting resistor R1 and the capacitance value of the DC blocking capacitor C1, the first voltage threshold can be adjusted, that is, the detected alternating current threshold is adjusted, so that only the alternating current exceeding the first voltage threshold can trigger the optocoupler to output a high level, otherwise it outputs a low level. By setting a suitable first voltage threshold, noise interference can be eliminated and the accuracy of detection can be improved.
[0040] Furthermore, in some embodiments, Figure 1 , Figure 2 , Figure 3 As shown, the optocoupler signal changing circuit also includes a pull-down resistor.
[0041] When the optical coupler includes only the first optical coupler U1, as Figure 2 , Figure 3 As shown, the pull-down resistor only includes a first pull-down resistor R21. One end of the first pull-down resistor R21 is connected to the emitter of the first phototransistor Q1, and the other end is grounded.
[0042] When the optical coupler includes a first optical coupler U1 and a second optical coupler U2, as shown in FIG. Figure 1As shown, the pull-down resistor includes not only the first pull-down resistor R21 but also a second pull-down resistor R22. One end of the second pull-down resistor R22 is connected to the emitter of the second phototransistor Q2, and the other end is grounded.
[0043] The first pull-down resistor R21 and the second pull-down resistor R22 can play a pull-down role when the first phototransistor Q1 and the second phototransistor Q2 are turned off, ensuring that the emitter will not float, thereby maintaining the output end at a certain low level state.
[0044] After the MCU module obtains the high and low level signals, it can calculate the pulse width, frequency, duty cycle and other information of the level through its internal timing counter, so as to determine whether AC power is entering according to the characteristics of the level signal.
[0045] In order to save costs, the MCU module uses an ordinary digital single-chip microcomputer, which can determine whether AC power is entering based on the duty cycle and frequency of the level signal.
[0046] Furthermore, the MCU module includes a timing counter and a processing unit.
[0047] The timing counter can measure the duration of the high level and / or low level of the level signal. The processing unit can determine the pulse width, frequency, period, duty cycle and other data of the AC power according to the data of the timing counter, and can count the number of events that meet the frequency and duty cycle conditions within a specific time window, so as to determine whether there is AC power intrusion according to preset conditions.
[0048] The preset conditions can be set as needed, and this embodiment does not limit them. For example, when the processing unit determines that the input frequency of the signal is between 35-65HZ, and this pattern is repeated multiple times within a certain time range, the processing unit can determine that it is AC intrusion. If the change is occasional, or the number is small, the processing unit will determine it as noise or disturbance, rather than the real intrusion of AC.
[0049] In order to verify the feasibility of the utility model, the applicant simulated the circuit structure, and the following is the simulation verification content:
[0050] 1. For the circuit structure of dual optocoupler: Figure 4 As shown, a 50HZ 220V AC power V2 and a 400V DC power V1 are connected in series to form a power supply to simulate the situation where AC enters the DC system. Oscilloscope channel 1 measures the DC bus voltage, and channels 3 and 4 are connected to the output ends of the dual optocouplers, namely the emitter of the first phototransistor Q1 and the emitter of the second phototransistor Q2.
[0051] It has been verified that the DC bus voltage amplitude measured by the oscilloscope reaches up to 707V, and its waveform is shown in purple at the adjacent Figure 5 The levels of channel 3 and channel 4 change alternately between 0V and 3.18V. The waveform of channel 3 is displayed in orange. Figure 5 In the figure, the waveform of channel 4 is displayed in blue. Figure 5 middle.
[0052] It can be seen that the optocoupler signal change circuit can directly convert the analog signal into a level signal, and it is easy for the MCU module to analyze the high and low level changes, such as frequency, pulse width, duty cycle, period, etc. through the timing counter.
[0053] 2. For the circuit structure of a single optocoupler: Figure 6 As shown, a 50HZ 220V AC power V2 and a 400V DC power V1 are connected in series to form a power supply to simulate the situation where AC enters the DC system. Oscilloscope channel 1 measures the DC bus voltage, channel 2 measures the AC voltage after isolating the DC component in the DC bus, and channel 3 is connected to the output end of the first optocoupler U1, that is, the emitter of the first phototransistor Q1.
[0054] It has been verified that the DC bus voltage amplitude measured by the oscilloscope reaches up to 707V, and its waveform is shown in purple at the adjacent Figure 7 The level of channel 3 changes alternately between 0V and 3.18V. The waveform of channel 3 is displayed in orange. Figure 7 In the figure, the waveform of channel 2 is displayed in green. Figure 7 middle.
[0055] It can be seen that the optocoupler signal change circuit can directly convert the analog signal into a level signal, and it is easy for the MCU module to analyze the high and low level changes, such as frequency, pulse width, duty cycle, period, etc. through the timing counter.
[0056] Although the present invention is disclosed through the above embodiments, the scope of the present invention is not limited thereto, and the above components may be replaced with similar or equivalent elements known to those skilled in the art without departing from the concept of the present invention.
Claims
1. A circuit for detecting AC-DC current leakage, characterized in that: It includes: DC blocking capacitor C1, used for connecting to the DC bus; An optocoupler signal changing circuit, used for converting an alternating current higher than a first voltage threshold into a level signal; the optocoupler signal changing circuit is provided with an optocoupler, and an input end of the optocoupler is connected to the DC blocking capacitor C1 and a ground end; The MCU module is connected to the output end of the optocoupler signal changing circuit and is used to determine whether there is AC current flowing in according to the level signal.
2. The AC-to-DC current detection circuit according to claim 1, wherein: The optocoupler signal changing circuit includes a first current limiting resistor R1 , and the input end of the optocoupler is connected to the DC blocking capacitor C1 via the first current limiting resistor R1 .
3. The AC-to-DC current detection circuit according to claim 2, wherein: The optical coupler includes a first optical coupler U1, and the first optical coupler U1 includes a first light emitting diode D1 and a first phototransistor Q1. The positive electrode of the first light emitting diode D1 is connected to the first current limiting resistor R1, and the negative electrode is connected to the ground terminal. The collector of the first phototransistor Q1 is connected to the positive electrode of the logic power supply, and the emitter is connected to the first port AC_N of the MCU module.
4. The AC-to-DC current detection circuit as claimed in claim 3, characterized in that: The optical coupler includes a second optical coupler U2, and the second optical coupler U2 includes a second light emitting diode D2 and a second phototransistor Q2. The anode of the second light emitting diode D2 is connected to the cathode of the first light emitting diode D1, and the cathode of the second light emitting diode D2 is connected to the anode of the first light emitting diode D1; The anode of the second phototransistor Q2 is connected to the anode of the logic power supply, and the emitter is connected to the second port of the MCU module.
5. The AC-to-DC current detection circuit as claimed in claim 3, characterized in that: The optocoupler signal changing circuit includes a third diode D3 , wherein an anode of the third diode D3 is connected to a cathode of the first light emitting diode D1 , and a cathode of the third diode D3 is connected to an anode of the first light emitting diode D1 .
6. The AC-to-DC current detection circuit as claimed in claim 5, characterized in that: The third diode D3 is a fast recovery diode.
7. The AC-DC current leakage detection circuit as claimed in any one of claims 3, 4 and 5, characterized in that: The emitter of the first phototransistor Q1 is connected to the first pull-down resistor R21 , and the other end of the first pull-down resistor R21 is grounded.
8. The AC-to-DC current detection circuit as claimed in claim 4, characterized in that: The emitter of the second phototransistor Q2 is connected to the second pull-down resistor R22, and the other end of the second pull-down resistor R22 is grounded.
9. The AC-to-DC current detection circuit as claimed in claim 2, characterized in that: The first voltage threshold is adjusted by the resistance value of the first current limiting resistor R1 and the capacitance value of the DC blocking capacitor C1.
10. The AC-to-DC current detection circuit according to claim 1, wherein: The MCU module includes: A timing counter, used for measuring the duration of the high level and / or low level of the level signal; The processing unit can determine at least one of the pulse width, frequency, period, and duty cycle data of the alternating current based on the data of the timing counter, and can count the number of events that meet the frequency and duty cycle conditions within a specific time window, and can determine whether there is alternating current intrusion based on preset conditions.