Micro-power-consumption self-recovery overvoltage, undervoltage and delay protection method and system

Abstract

The invention discloses a micro-power-consumption self-recovery overvoltage, undervoltage and delay protection method and system, and relates to the technical field of power protection. The method comprises the following steps of: isolating and sampling alternating current voltage through a voltage transformer, wherein the primary side of the transformer is connected in series with a 150-400K omega current-limiting resistor; 1 kHz ADC sampling is carried out by adopting an 8-bit single chip microcomputer; the voltage true RMS is calculated by adopting integer operation every 100ms, and a floating point operation unit is not needed; three-state machine control logic is executed according to the voltage state, a relay is released immediately when abnormity occurs, and pull-in is delayed for 10 seconds after the relay returns to normal; the magnetic latching relay is driven by double pulses. The system comprises a power supply module, a voltage sampling module, a main control module and a relay driving module, wherein the power supply module adopts a hybrid voltage stabilization framework. The standby power consumption of the whole machine is less than or equal to 0.5 W, and the power consumption configuration of 0.24-0.46 W is realized by selecting different current-limiting resistors and is reduced by 62-84% compared with that of a traditional product; the measurement precision is + / -1V at 220V, and the linearity is + / -0.1%; a voltage return difference mechanism and delayed reset are adopted, so that power grid fluctuation misoperation is effectively prevented; the magnetic latching relay keeps the state with zero power consumption, and the mechanical life is greater than 1 million times. The power supply protection circuit is suitable for household and small equipment power supply protection application.

Description

Technical Field

[0001] This invention relates to the field of power protection technology, and in particular to a low-power self-resetting overvoltage and undervoltage delay protection method and system. Background Technology

[0002] Traditional household voltage protector power supply solutions mainly include the following:

[0003] 1. High-voltage section uses RC step-down: low cost but high power consumption, usually 1W-1.5W, serious heat generation, poor safety;

[0004] 2. The low-voltage section uses a high-power load resistor and Zener diode to step down and regulate the voltage, but the load resistor and Zener diode consume a lot of power;

[0005] 3. Full DC-DC conversion scheme: High efficiency but high cost. Under light load (less than 5mA) conditions, the efficiency advantage of the two-stage DC-DC chip is not obvious, and it increases noise and external components.

[0006] Disadvantages of existing technology:

[0007] 1. High standby power consumption, significant heat generation during prolonged power-on, annual power consumption is approximately 7-13 kWh;

[0008] 2. The power supply solution is not optimized for light-load conditions, resulting in a mismatch between cost and performance;

[0009] 3. Using operational amplifier voltage comparison results in low measurement accuracy (only ±5-10V) and poor anti-interference capability.

[0010] 4. Relays need to be energized for a long time to remain engaged, resulting in high power consumption and a mechanical life of only about 100,000 cycles;

[0011] 5. Without a voltage hysteresis mechanism, it is prone to malfunction when the power grid fluctuates.

[0012] According to JGJ 242-2011 "Code for Electrical Design of Residential Buildings" and GB 50368 "Code for Design of Residential Buildings", each residential unit should be equipped with self-restoring over and undervoltage protection devices.

[0013] Therefore, there is an urgent need for a self-resetting overvoltage and undervoltage protection method and system with low power consumption, high precision, and long lifespan. Summary of the Invention

[0014] The technical problem to be solved by the present invention is to provide a self-resetting overvoltage and undervoltage delay protection method and system with low power consumption, low temperature rise, high precision, and long life.

[0015] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0016] A low-power self-resetting overvoltage and undervoltage delay protection method and system includes the following steps:

[0017] S1: The AC voltage is sampled in isolation by a voltage transformer. The primary winding of the transformer is connected in series with a current-limiting resistor, and the secondary winding is connected in parallel with a load resistor.

[0018] S2: An 8-bit microcontroller is used to perform ADC conversion on the sampled signal, with a sampling frequency of 1kHz;

[0019] S3: Calculate the true RMS voltage value every 100ms, using integer arithmetic to calculate the square root;

[0020] S4: Determine the voltage status based on the true effective value of the voltage, including normal status, abnormal status and delayed status;

[0021] S5: In abnormal conditions, immediately execute the release action of the magnetic latching relay;

[0022] S6: After the voltage returns to normal from the abnormal state, the delay count is started, during which the relay remains in the released state;

[0023] S7: After the delay count ends, the magnetic latching relay is activated.

[0024] The method described above results in a standby power consumption of ≤0.5W for the entire device.

[0025] Further, in step S1, the resistance of the current-limiting resistor is 150KΩ-400KΩ, and the resistance of the load resistor is 50Ω-1KΩ.

[0026] Furthermore, the current-limiting resistor has a resistance of 200KΩ, the load resistor has a resistance of 680Ω, the primary operating current of the current transformer is 0.5mA-1.5mA, and the system standby power consumption is 0.38W.

[0027] Furthermore, in step S3, the formula for calculating the true RMS value of the voltage is:

[0028] Vrms = √[Σ(Vi-Vdc)² / N] × K

[0029] Where Vi is the ADC sample value, Vdc is the DC bias ADC value, N is the number of sampling points, and K is the scaling factor.

[0030] Furthermore, the scaling factor K is determined based on the resistance value of the primary current-limiting resistor. When the current-limiting resistor is 150KΩ, K=85; when the current-limiting resistor is 200KΩ, K=115; when the current-limiting resistor is 300KΩ, K=175; and when the current-limiting resistor is 400KΩ, K=235.

[0031] Furthermore, the scaling coefficient K is determined by the following formula:

[0032] K = Ratio_system × Vref_mV / 10240

[0033] Where Ratio_system is the measured system ratio, and Vref_mV is the millivolt value of the ADC reference voltage.

[0034] Further, in step S4, the normal state is when the voltage is in the range of 180V-250V and the relay is in the energized state; the abnormal state is when the voltage is less than 180V or greater than 250V, and the relay is immediately released; the delay state is when the voltage recovers from the abnormal state to normal, a 10-second delay count is started, during which the relay remains released.

[0035] Furthermore, in step S4, a voltage hysteresis mechanism is used to prevent frequent operation caused by voltage fluctuations. The undervoltage protection point is 180V, the undervoltage recovery point is 185V, the overvoltage protection point is 250V, and the overvoltage recovery point is 245V.

[0036] Furthermore, in steps S5 and S7, the magnetic latching relay is driven in a dual-pulse mode, with each pulse width being 100ms and the interval between the two pulses being 50ms.

[0037] Furthermore, in step S3, integer arithmetic is used to calculate the square root. Specifically, this includes using a 32-bit unsigned integer to store the sum of squares of the AC components and using a bit-by-bit trial-and-error method to calculate the square root. The entire process does not involve floating-point arithmetic instructions.

[0038] Furthermore, in step S2, a timer interrupt is used to trigger ADC sampling. The interrupt period is 1ms, and 100 points are sampled continuously and stored in a circular buffer. After sampling is completed, the ready flag is set, and the main loop queries the flag to process the data.

[0039] Furthermore, it also includes a testing step, in which a set DC voltage is applied to the ADC detection circuit via a test button to simulate an abnormal voltage state.

[0040] Furthermore, it also includes an alarm procedure, which uses a buzzer to issue an alarm notification in the event of undervoltage, overvoltage, or delay.

[0041] Enter

[0042] Further, it also includes a display step, which uses LEDs to display voltage range values ​​and relay status.

[0043] A low-power self-resetting overvoltage and undervoltage delay protection system for implementing the above method includes:

[0044] The power module is used to convert the AC 220V input into DC operating power.

[0045] The voltage sampling module uses a voltage transformer for isolated sampling. Its primary winding has a current-limiting resistor connected in series, and its secondary winding has a load resistor connected in parallel.

[0046] The main control module uses an 8-bit microcontroller and is connected to the voltage sampling module and the power supply module;

[0047] A relay drive module, connected to the main control module, is used to drive a magnetic latching relay;

[0048] The system's standby power consumption is ≤0.5W.

[0049] Furthermore, the power supply module includes a rectifier circuit, a first-stage DC-DC converter circuit, and a second-stage linear regulator circuit. The first-stage DC-DC converter circuit converts the rectified high-voltage DC power into a 12V DC intermediate voltage, and the second-stage linear regulator circuit converts the 12V DC intermediate voltage into a 3.3V DC operating voltage.

[0050] Furthermore, the first-stage DC-DC converter circuit uses a low-power primary-side integrated chip, eliminating the need for optocoupler feedback and achieving a conversion efficiency of ≥80%.

[0051] Furthermore, the second-stage linear regulator circuit uses a three-terminal regulator with an input voltage range of 5V-30V, an output voltage of 3.3V±5%, and a quiescent current ≤5mA.

[0052] Furthermore, the resistance of the current-limiting resistor is 150KΩ-400KΩ. By selecting different resistance values ​​of the current-limiting resistor, the power consumption and accuracy can be configured, and the system standby power consumption is 0.24W-0.46W.

[0053] Furthermore, the 8-bit microcontroller has a built-in 10-bit ADC, which calculates the true effective value through the integer square root algorithm, eliminating the need for a floating-point arithmetic unit.

[0054] Furthermore, it also includes a status indication module, which includes LEDs and a buzzer for indicating voltage range, relay status, and abnormal status.

[0055] Furthermore, the magnetic latching relay is provided with a manual operating mechanism, which includes a manual operating push rod disposed in the relay housing, capable of forcibly disconnecting or connecting the power supply.

[0056] The beneficial effects of this invention are:

[0057] 1. It is the first to implement the true effective value algorithm of integers on an 8-bit microcontroller, without the need for a floating-point arithmetic unit, which has fast calculation speed, high precision, and RAM usage of less than 100 bytes;

[0058] 2. By selecting a primary current-limiting resistor ranging from 150KΩ to 400KΩ, flexible configuration of power consumption and accuracy can be achieved. Standby power consumption is selectable from 0.24W to 0.46W, which is 62-84% lower than traditional products.

[0059] 3. The three-state machine control logic, combined with a 10-second delay reset and voltage hysteresis mechanism, effectively prevents malfunctions caused by power grid fluctuations;

[0060] 4. The magnetic latching relay is driven by a dual-pulse mechanism, ensuring reliable operation, zero power consumption in the holding state, and a mechanical life of more than 1 million cycles;

[0061] 5. Hybrid voltage regulator architecture: DC-DC converter on the high-voltage side ensures efficiency, while linear regulation on the low-voltage side is optimized for light-load conditions, reducing costs by 50% and lowering noise.

[0062] 6. The standby power consumption of the whole machine is ≤0.5W, the main solution is 0.38W, and the annual power saving is about 4-10 kWh. If it is promoted nationwide, the annual power saving will exceed 5 billion kWh.

[0063] 7. Measurement accuracy ±1V@220V, linearity ±0.1%, 5-10 times higher than traditional products;

[0064] 8. No ambient temperature rise; the casing temperature rise is less than 2°C after 2 hours of continuous operation.

[0065] 9. Low cost, with a BOM cost of approximately 30 yuan, suitable for large-scale applications;

[0066] 10. Add test buttons and buzzer alarms to improve equipment reliability and user experience. Attached Figure Description

[0067] Figure 1 is a system block diagram of the present invention;

[0068] Figure 2 is a circuit schematic diagram of the present invention;

[0069] Figure 3 is a circuit diagram of the power module of the present invention;

[0070] Figure 4 is a software flowchart of the present invention;

[0071] Figure 5 is a state transition diagram of the three-state machine of the present invention;

[0072] Figure 6 is a structural diagram of the present invention and a schematic diagram of the manual operation mechanism;

[0073] Figure 7 is a schematic diagram of the test button and relay working status indication of the present invention. Detailed Implementation

[0074] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0075] Example 1 (Main scheme: 200KΩ primary resistor)

[0076] The low-power self-resetting AC voltage protection method of this embodiment includes the following steps:

[0077] Step S1: Isolate and sample the AC voltage using a ZMPT107-1 voltage transformer. A 200KΩ / 1W current-limiting resistor is connected in series on the primary side of the transformer, and a 680Ω / 1 / 4W load resistor is connected in parallel on the secondary side. The primary operating current of the transformer is 1.086mA.

[0078] Step S2: Use an STM8S003F3P6 microcontroller to perform 10-bit ADC conversion on the sampled signal. Timer 2 generates a 1ms interrupt, and the ADC value is read once each time. The sampling frequency is 1kHz.

[0079] Step S3: Calculate the true RMS voltage value every 100ms, using integer arithmetic to calculate the square root. The calculation formula is as follows:

[0080] Vrms = √[Σ(Vi-507)² / 100] × 115 / 100

[0081] 507 is the DC bias ADC value, and 115 is the scaling factor.

[0082] The integer operation specifically includes: storing the sum of squares using a 32-bit unsigned integer, calculating the square root using a bit-by-bit trial method, with the initial trial bit being 2 to the power of 30, shifting right by 2 bits in each iteration until the trial bit is 0, the entire process does not involve floating-point operation instructions, and the execution time is less than 1ms.

[0083] Step S4: Determine the voltage state based on the true effective value of the voltage, using a three-state machine control logic:

[0084] Normal state: When the voltage is within the range of 180V-250V, the relay is engaged and the green light is constantly on;

[0085] Abnormal state: If the voltage is less than 180V or greater than 250V, the relay will immediately release and the red light will remain on.

[0086] Delay state: After the voltage recovers from the abnormal state, a 10-second delay count is started, during which the relay remains released and the red light flashes at a frequency of 0.5Hz.

[0087] A voltage hysteresis mechanism is adopted to prevent frequent operation caused by voltage fluctuations. The undervoltage protection point is 180V, the undervoltage recovery point is 185V, the overvoltage protection point is 250V, and the overvoltage recovery point is 245V.

[0088] Step S5: In abnormal conditions, immediately execute the release action of the magnetic latching relay, using a dual-pulse drive method, with the first pulse lasting 100ms and an interval of 50ms, and the second pulse lasting 100ms.

[0089] Step S6: After the voltage returns to normal from the abnormal state, start a 10-second delay count, during which the relay remains in the released state.

[0090] Step S7: After the delay count is completed, the magnetic latching relay is activated using a dual-pulse drive method.

[0091] Step S8: Using the test button, connect the set DC voltage to the ADC detection circuit. After the ADC acquires the data and the system calculates it, simulate an abnormal primary voltage of the current transformer to test whether the protector operates normally.

[0092] Step S9: Set up a buzzer to alert for abnormal voltage conditions, emitting alarm sounds of different frequencies and frequencies under different alarm conditions.

[0093] Step S10: Based on the set voltage, display the voltage range value using LEDs and indicate the relay status using two LEDs.

[0094] The power module adopts a hybrid voltage regulation architecture:

[0095] Rectifier circuit: 220V AC power is rectified into 310V DC power by VMB10S rectifier bridge;

[0096] First-stage DC-DC converter: Utilizing the BP8595D low-power primary-side integrated chip, it converts 310V DC to 12V DC without requiring optocoupler feedback, achieving a conversion efficiency of ≥80%.

[0097] The second stage of linear regulation uses a 78L33 three-terminal regulator to convert 12V DC to 3.3V DC. Because the MCU's operating current is only 1.5mA, the power consumption of the linear regulator is approximately 13mW, comparable to a DC-DC solution, but with lower cost and less noise. A 22μF capacitor is connected in parallel at the output.

[0098] De-capacitor and 100nF ceramic capacitor for filtering.

[0099] Test data:

[0100] Standby power consumption: 0.38W;

[0101] Measurement accuracy: ±1V@220V;

[0102] Linearity: ±0.095%;

[0103] Temperature rise test: less than 2℃;

[0104] Response time: less than 400ms;

[0105] Reset delay: 10 seconds;

[0106] Relay operation success rate: 100% success rate in 10,000 tests.

[0107] Example 2 (Low power solution: 400KΩ primary resistor)

[0108] The difference between this embodiment and Embodiment 1 is that in step S1, the primary current-limiting resistor is 400KΩ / 1 / 2W, the primary operating current of the current transformer is 0.536mA, the scaling factor K=235 in step S3, and the standby power consumption of the whole machine is 0.24W.

[0109] To evaluate the performance of different current-limiting resistor schemes, the project team conducted systematic tests on four schemes: 150KΩ, 200KΩ, 300KΩ, and 400KΩ. Due to the use of a single-head multimeter for step-by-step measurements, the measurement errors mainly included timing errors, instrument errors, reading errors, and environmental interference, with a combined error of ±0.87%.

[0110] The data was processed using a weighted average method, with weights assigned according to the engineering importance of each voltage point: 220V with a weight of 0.35, 200V and 240V each with a weight of 0.15, and 180V and 250V each with a weight of 0.10. The calculated weighted average multiples for the four schemes were 262.10, 350.93, 525.46, and 703.35, respectively, with weighted standard deviations of 0.105, 0.189, 0.312, and 0.387, respectively.

[0111] After considering measurement system errors, the corrected linearity is ±0.87%. Based on the formula K = (multiplier multiplied by Vref_mV) divided by 10240, the theoretical scaling coefficients are calculated to be 85.52, 114.51, 171.45, and 229.49, respectively. For engineering applications, it is recommended to round these values ​​to 85, 115, 172, and 230. 95% confidence interval analysis shows that the 200KΩ scheme performs best in terms of accuracy and stability; therefore, it is selected as the primary scheme.

[0112] Example 3 (High-precision solution: 150KΩ primary resistor)

[0113] The difference between this embodiment and Embodiment 1 is that in step S1, the primary current-limiting resistor is 150KΩ / 1W, the primary operating current of the current transformer is 1.45mA, the scaling factor K=85 in step S3, and the standby power consumption of the whole machine is 0.46W.

[0114] Example 4 (Detailed Description of Software Logic Implementation)

[0115] The software program in this embodiment is stored in the FLASH memory of the STM8S003F3P6 microcontroller and adopts a modular design. It mainly includes the main program, timer interrupt service routine, voltage calculation algorithm and relay control state machine.

[0116] 4.1 Main Program Flow

[0117] After the system is powered on, the GPIO, ADC and timer modules are initialized first;

[0118] Execute the power-on LED self-test sequence;

[0119] Pre-fill the ADC buffer with 100 points;

[0120] Enable global interrupts and enter the main loop;

[0121] In the main loop, query the sampling ready flag, sample_ready;

[0122] If the flag is 1, then the voltage calculation function and the relay control function are called;

[0123] After processing is complete, the flag is cleared, the WFI instruction is executed to enter low-power sleep mode, and the system waits for a timer interrupt to wake it up.

[0124] 4.2 Algorithm for True RMS Voltage Value

[0125] The timer interrupt is triggered every 1ms, reading the ADC value and storing it in the buffer;

[0126] RMS calculation is performed every 100ms (100 points);

[0127] The calculation process is as follows:

[0128] a) Traverse 100 sampling points and subtract the DC bias value of 507;

[0129] b) Calculate the squares of the differences and sum them to the 32-bit variable sum_squares;

[0130] c) Calculate the average: mean_square = sum_squares / 100;

[0131] d) Call the integer_Sqrt function to calculate the square root;

[0132] e) Multiply by the scaling factor 115, divide by 100, and get the voltage value (unit: 0.1V).

[0133] The entire calculation process involves pure integer operations, with no floating-point instructions, and the execution time is less than 1ms.

[0134] 4.3 Relay Control State Machine

[0135] Define three states: STATE_NORMAL(0), STATE_ABNORMAL(1), STATE_DELAYING(2);

[0136] State transition logic:

[0137] If the current state is normal, and the voltage is less than 180V or greater than 250V, then switch to the abnormal state and immediately execute the release action;

[0138] If the current state is abnormal, and the voltage recovers to between 185V and 245V, then jump to the delay state and start a 10-second counter;

[0139] If the current state is a delay state, the counter will jump to the normal state after 10 seconds and perform the engagement action.

[0140] Setting the action_executing flag blocks state changes during the action to prevent repeated triggering.

[0141] 4.4 Dual-Pulse Drive Logic

[0142] When the relay is activated, it outputs a high level for 100ms;

[0143] Output is turned off for 50ms;

[0144] Output a high level again for 100ms;

[0145] Output is off; action complete.

[0146] This logic ensures reliable operation of the magnetic latching relay and avoids failure on a single pulse.

[0147] Example 5 (Socio-economic benefit analysis)

[0148] According to the JGJ 242-2011 standard, each residential unit should be equipped with a self-resetting over / under voltage protector. According to publicly available data from the National Energy Administration, as of the end of 2024, there were approximately 700 million electricity users nationwide.

[0149] Assuming all 700 million electricity users nationwide adopt this product to replace traditional products (traditional products have a standby power consumption of 1.2W, while this product's main solution has a standby power consumption of 0.38W):

[0150] Annual electricity savings per household:

[0151] ΔP = 1.2W - 0.38W = 0.82W

[0152] E_single = 0.82W × 24h × 365 days = 7.1832 kWh / year

[0153] National annual electricity savings:

[0154] E_save = 700 million households × 7.1832 kWh / year = 5.04 billion kWh / year

[0155] Economic benefits:

[0156] Based on a residential electricity price of 0.5-0.6 yuan / kWh,

[0157] Economic benefits = 5.04 billion kWh × 0.5 yuan / kWh = 2.52 billion yuan / year

[0158] Taking Qingzhen City, Guizhou Province as an example:

[0159] The county has approximately 155,000 households (data from the Guizhou Provincial Bureau of Statistics). If all of them were to install:

[0160] Qingzhen City's annual electricity savings:

[0161] E_local = 155,000 households × 7.1832 kWh / year = 1,113,400 kWh / year

[0162] Economic benefits of Qingzhen City:

[0163] Economic benefit = 1,113,400 kWh × 0.5 yuan / kWh = 556,700 yuan / year

[0164] Social benefits:

[0165] Extending equipment lifespan, the mechanical life of magnetic latching relays exceeds 1 million cycles, which is 10 times that of traditional relays;

[0166] Improved power supply reliability and self-resetting design eliminates the need for manual reset, making it particularly suitable for scenarios where no one is home.

[0167] To reduce the risk of fire, immediately disconnect the power supply in case of abnormal voltage to prevent electrical fires;

[0168] Promote technological innovation and provide new technical solutions for power protection equipment.

[0169] Example 6 (Determination and calibration of scaling coefficient K)

[0170] The scaling factor K is used to convert the RMS calculation result in ADC units to a primary voltage value in 0.1V units. Its calculation formula is as follows:

[0171] K = Ratio_system × Vref_mV / 10240

[0172] in:

[0173] Ratio_system is the measured system ratio, obtained by the ratio of the measured primary voltage to the AC signal voltage at the ADC input. For example, in a 150KΩ scheme, when the input is 220V, the ADC input signal is 0.8397V, then Ratio_system = 220 / 0.8397 ≈ 262.

[0174] Vref_mV is the millivolt value of the ADC reference voltage, which is 3341.2mV in actual measurement.

[0175] 10240 is the product of the 10-bit ADC resolution (1024) and the voltage unit conversion factor (10).

[0176] Substitute the measured values:

[0177] 150KΩ solution: K = 262 × 3341.2 / 10240 ≈ 85.5, rounded down to 85;

[0178] 200KΩ solution: K = 351 × 3341.2 / 10240 ≈ 114.5, rounded down to 115;

[0179] 300KΩ solution: K = 525 × 3341.2 / 10240 ≈ 171.3, rounded down to 172;

[0180] 400KΩ solution: K = 703 × 3341.2 / 10240 ≈ 229.4, rounded down to 230.

[0181] Due to batch variations in component parameters, it is recommended to use the actual measurement calibration method:

[0182] Input standard 220.0V AC voltage;

[0183] Read the RMS calculation result rms_value;

[0184] Calculate K = 2200 × 100 / rms_value;

[0185] Use after rounding, and verify the accuracy of the 180V / 250V two-point test.

[0186] Actual calibration can eliminate the influence of factors such as batch differences in components and temperature drift, ensuring measurement accuracy.

[0187] Example 7 (Testing and Verification Methods)

[0188] To ensure the reliability and accuracy of the protector of this invention, the following testing and verification methods were established:

[0189] 7.1 Power Consumption Test

[0190] Test equipment: Power analyzer (accuracy 0.5%)

[0191] Test conditions:

[0192] Input voltage: 220V AC 50Hz

[0193] Ambient temperature: 25℃

[0194] Relay status: Engaged

[0195] Test steps:

[0196] Connect the protector to the power analyzer;

[0197] Record the power reading in standby mode;

[0198] Take 10 consecutive measurements and calculate the average value.

[0199] Four solutions with 150KΩ, 200KΩ, 300KΩ, and 400KΩ were tested respectively.

[0200] 7.2 Accuracy Test

[0201] Test equipment: Adjustable AC power supply (0-300V AC), high-precision digital multimeter (accuracy 0.05%)

[0202] Test conditions:

[0203] Ambient temperature: 25℃

[0204] Test voltage points: 180V, 200V, 220V, 240V, 250V

[0205] Test steps:

[0206] Adjust the adjustable power supply to the test voltage point;

[0207] Use a high-precision multimeter to confirm the actual voltage value;

[0208] Read the voltage value displayed on the protector;

[0209] Error calculation: Error = (Displayed value - Actual value) / Actual value × 100%;

[0210] Measure each voltage point 5 times and take the average value.

[0211] 7.3 Response Time Test

[0212] Test equipment: Oscilloscope (100MHz bandwidth)

[0213] Test steps:

[0214] Connect the voltage surge signal to oscilloscope channel 1;

[0215] Oscilloscope channel 2 is connected to the relay control signal;

[0216] Triggering undervoltage or overvoltage conditions;

[0217] Measure the time difference between a voltage surge and the relay action;

[0218] Repeat the test 10 times and take the maximum value.

[0219] 7.4 Temperature Rise Test

[0220] Testing equipment: Infrared thermometer

[0221] Test steps:

[0222] The protector operates continuously for 2 hours;

[0223] Measure the casing temperature every 30 minutes;

[0224] Record the highest temperature increase;

[0225] Ambient temperature is used as the reference.

[0226] 7.5 Relay Life Test

[0227] Test steps:

[0228] Set the voltage cycle: 220V→260V→220V;

[0229] Automatically record the number of actions;

[0230] Contact resistance is tested every 100,000 times;

[0231] Record the number of failures.

[0232] The above testing methods ensure that the performance indicators of the protector of this invention meet the design requirements, providing quality assurance for mass production.

[0233] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-power self-resetting overvoltage and undervoltage delay protection method and system, characterized in that, Includes the following steps: S1: The sampled AC voltage is isolated by a voltage transformer, wherein the primary winding of the transformer is connected in series with a current-limiting resistor. The secondary winding has a load resistor connected in parallel; S2: An 8-bit microcontroller is used to perform ADC conversion on the sampled signal, with a sampling frequency of 1kHz; S3: Calculate the true RMS voltage value every 100ms, using integer arithmetic to calculate the square root; S4: Determine the voltage status based on the true effective value of the voltage, including normal status, abnormal status and delayed status; S5: In abnormal conditions, immediately execute the release action of the magnetic latching relay; S6: After the voltage returns to normal from the abnormal state, the delay count is started, during which the relay remains in the released state; S7: After the delay count ends, the magnetic latching relay is activated. The method described above results in a standby power consumption of ≤0.5W for the entire device.

2. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 1, characterized in that: In step S1, the resistance of the current-limiting resistor is 150KΩ-400KΩ, and the resistance of the load resistor is... 50Ω-1KΩ.

3. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 2, characterized in that: The current-limiting resistor has a resistance of 200KΩ, the load resistor has a resistance of 680Ω, the primary operating current of the current transformer is 0.5mA-1.5mA, and the system standby power consumption is 0.38W.

4. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 1, characterized in that: In step S3, the formula for calculating the true RMS value of the voltage is: Vrms = √[Σ(Vi-Vdc)² / N] × K Where Vi is the ADC sample value, Vdc is the DC bias ADC value, N is the number of sampling points, and K is the scaling factor.

5. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 4, characterized in that: The scaling factor K is determined based on the resistance value of the primary current-limiting resistor. When the current-limiting resistor is 150KΩ, K=85; when the current-limiting resistor is 200KΩ, K=115; when the current-limiting resistor is 300KΩ, K=175; and when the current-limiting resistor is 400KΩ, K=235.

6. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 4, characterized in that: The scaling factor K is determined by the following formula: K = Ratio_system × Vref_mV / 10240, where Ratio_system is the measured system magnification and Vref_mV is the millivolt value of the ADC reference voltage.

7. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 1, characterized in that: In step S4, the normal state is when the voltage is in the range of 180V-250V and the relay is in the energized state; The abnormal state is when the voltage is less than 180V or greater than 250V, in which case the relay will be immediately released; The delay state is defined as follows: after the voltage recovers from an abnormal state, a 10-second delay count is initiated, during which the relay remains released.

8. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 7, characterized in that: In step S4, a voltage hysteresis mechanism is used to prevent frequent operation caused by voltage fluctuations. The undervoltage protection point is... 180V, undervoltage recovery point is 185V, overvoltage protection point is 250V, and overvoltage recovery point is 245V.

9. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 1, characterized in that: In steps S5 and S7, the magnetic latching relay is driven in a dual-pulse mode, with each pulse width being 100ms and the interval between the two pulses being 50ms.

10. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 1, characterized in that: In step S3, integer arithmetic is used to calculate the square root. Specifically, this includes using a 32-bit unsigned integer to store the sum of squares of the AC components and using a bit-by-bit trial-and-error method to calculate the square root. The entire process does not involve floating-point arithmetic instructions.

11. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 1, characterized in that: In step S2, a timer interrupt is used to trigger ADC sampling. The interrupt period is 1ms. 100 points are sampled continuously and stored in a circular buffer. After sampling is completed, the ready flag is set. The main loop queries the flag to process the data.

12. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 1, characterized in that: It also includes a test procedure, in which a set DC voltage is applied to the ADC detection circuit via a test button to simulate an abnormal voltage state.

13. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 1, characterized in that: It also includes an alarm procedure, which uses a buzzer to issue an alarm prompt in the event of undervoltage, overvoltage, or delay.

14. The low-power self-resetting overvoltage and undervoltage delay protection method according to claim 1, characterized in that: It also includes a display step, which uses LEDs to display voltage range values ​​and relay status.

15. A low-power self-resetting overvoltage and undervoltage delay protection system, used to implement any one of claims 1-14. The method is characterized in that, include: The power module is used to convert the AC 220V input into DC operating power. The voltage sampling module uses a voltage transformer for isolated sampling. Its primary winding has a current-limiting resistor connected in series, and its secondary winding has a load resistor connected in series. The main control module uses an 8-bit microcontroller and is connected to the voltage sampling module and the power supply module; A relay drive module, connected to the main control module, is used to drive a magnetic latching relay; The system's standby power consumption is ≤0.5W.

16. The low-power self-resetting overvoltage and undervoltage delay protection system according to claim 15, characterized in that: The power module includes a rectifier circuit, a first-stage DC-DC converter circuit, and a second-stage linear regulator circuit. The first-stage DC-DC converter circuit converts the rectified high-voltage DC power into a 12V DC intermediate voltage. The second-stage linear regulator circuit converts the 12V DC intermediate voltage into a 3.3V DC operating voltage.

17. The low-power self-resetting overvoltage and undervoltage delay protection system according to claim 16, characterized in that: The first-stage DC-DC converter circuit uses a low-power primary-side integrated chip, requires no optocoupler feedback, and has a conversion efficiency of ≥80%.

18. The low-power self-resetting overvoltage and undervoltage delay protection system according to claim 16, characterized in that: The second-stage linear regulator circuit uses a three-terminal regulator with an input voltage range of 5V-30V, an output voltage of 3.3V±5%, and a quiescent current ≤5mA.

19. The low-power self-resetting overvoltage and undervoltage delay protection system according to claim 15, characterized in that: The current-limiting resistor has a resistance value of 150KΩ-400KΩ. By selecting different resistance values ​​of the current-limiting resistor, the power consumption and accuracy can be configured. The system standby power consumption is 0.24W-0.46W.

20. The low-power self-resetting overvoltage and undervoltage delay protection system according to claim 15, characterized in that: The 8-bit microcontroller has a built-in 10-bit ADC and uses the integer square root algorithm to calculate the true effective value, eliminating the need for a floating-point arithmetic unit.

21. The low-power self-resetting overvoltage and undervoltage delay protection system according to claim 15, characterized in that: It also includes a status indication module, which includes LEDs and a buzzer for indicating voltage range, relay status and abnormal status.

22. The low-power self-resetting overvoltage and undervoltage delay protection system according to claim 15, characterized in that: The magnetic latching relay is equipped with a manual operating mechanism, which includes a manual operating push rod disposed in the relay housing, capable of forcibly disconnecting or connecting the power supply.

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