Diode-based system protection circuit

Abstract

The utility model relates to a system protection circuit based on a diode. The system protection circuit comprises an RC loop, a diode DN16, capacitors CN28 and CN31, and an aluminum electrolytic capacitor EN9. The RC loop is electrically connected with a jig inductor LN5; the capacitors CN28 and CN31 are connected in parallel with the two ends of the jig inductor LN5; the input ends of the capacitors CN28 and CN31 are connected with an SPS + 18V; and the SPS + 18V is also connected with a voltage MHVDD through a diode DN16. The device is reasonable in design, compact in structure and convenient to use.

Description

Technical Field

[0001] The utility model relates to a diode-based system protection circuit, in particular to the field of intelligent electric meter protection circuits. Background Art

[0002] The IO port is the pin for the integrated circuit chip to input / output digital / analog signals. At present, the IO port of most MCU chips can withstand a maximum voltage of about 5.5V. However, in the power detection circuit in the application field of electric energy meters, the voltage of the IO port often exceeds the maximum voltage range that the IO port of the chip itself can withstand while meeting the requirements of various technical indicators. There are two main solutions to this problem: one is to reduce the redundancy of technical indicators; the other is to adjust the parameters of the switching power supply transformer. The method in Chinese patent 201810022994.5 has obvious defects. When reducing the redundancy of technical indicators, the reliability is reduced. When adjusting the parameters of the transformer, the workload is quite large. After the adjustment, a series of data indicator verifications need to be done multiple times. Moreover, different MCUs will present different situations, resulting in poor versatility of the transformer. If a balance point is selected, this greatly increases the research and development cycle. Therefore, it is urgent to develop and design an IO port protection circuit with low cost, high versatility, short design time cycle and suitable for MCUs with different thresholds to achieve good social value and economic benefits.

[0003] The IO port in the MCU system is the pin for the integrated circuit chip to input and output digital signals and analog signals. At present, the maximum voltage that the IO port of most MCU systems can withstand is about 5.5V. In the field of smart meters, an IO port is usually used to detect the voltage on and off of the system. Under the premise of meeting various technical indicators, if the voltage at power-on fluctuates, the voltage detected at power-on may exceed the maximum input voltage of the system. Exceeding the maximum system input voltage will cause the system to fail to work normally. It is a very important task to protect the normal operation of the system circuit, especially in the power-on and power-off voltage detection of smart meters. The normal operation of the MCU system is an indispensable part of smart meters in measurement, communication, display, etc. In summary, the protection circuit of the system is particularly important.

[0004] The power-on and power-off voltage detection circuit of the existing MCU system is shown in the attached figure. This circuit uses a relatively simple resistor voltage division form to detect the power-on and power-off voltages. VIN is the direct current output by the AC-DC after the smart meter is powered on. VIN outputs the voltage VOUT after the resistors R2 and R3 divide the voltage. VOUT is directly connected to the pin of the MCU system. The voltage value at the VOUT point is used to determine whether it is in the power-on state or the power-off state. The formula for calculating the power-on and power-off voltage detection pins is as follows:

[0005]

[0006] However, this circuit has the following disadvantages: 1. If it is directly connected to the MCU system end without a filter capacitor, the detected voltage may be interfered with by the outside world and may be inaccurate. 2. If the voltage value of VIN is higher, the voltage value obtained by resistor voltage division will be larger. In this case, the voltage value of the IO port may exceed the threshold of the MCU, causing damage to the MCU system. 3. Poor versatility, long R&D cycle, and large workload. Utility Model Content

[0007] The technical problem to be solved by the utility model is generally to provide a diode-based system protection circuit. The diode-based system protection circuit is suitable for MCU systems (micro control units) with different thresholds, and is usually used in the power-up and power-down detection circuits of smart meters, achieving low cost, high versatility, short design cycle, and suitability for MCUs with different thresholds.

[0008] In order to solve the above problems, the technical solution adopted by the utility model is:

[0009] In order to achieve low cost and high versatility, the utility model provides a diode-based system protection circuit, including an RC loop, a diode DN16, capacitors CN28 and CN31, and an aluminum electrolytic capacitor EN9;

[0010] The RC loop is electrically connected with an industrial mode inductor LN5;

[0011] Capacitors CN28 and CN31 are connected in parallel at both ends of the industrial mode inductor LN5;

[0012] Connect SPS+18V to the input terminals of capacitors CN28 and CN31;

[0013] SPS+18V is also connected to voltage MHVDD through diode DN16.

[0014] In order to achieve filtering, the RC circuit includes resistor RN34, capacitors CN26, CN30, CN32, and rectifier diode DN15;

[0015] One end of the resistor RN34 is used to connect to the auxiliary terminal SPSO of the AC-DC switching power supply transformer; the other end of the resistor RN34 is connected to the ground through the capacitor CN26 and then through the parallel capacitors CN30 and CN32. The series resistor RN34, capacitor CN26 and rectifier diode DN15 are connected in parallel.

[0016] In order to achieve a short cycle and be suitable for MCUs with different thresholds, the voltage connection point of SPS+18V is electrically connected to resistors RT6 and RT7 in series, the other end of resistor RT7 is electrically connected to one end of resistor RT8, the other end of resistor RT8 is connected to GND, and one end of resistor RT8 is electrically connected to one end of capacitor CT7; capacitors CT7 and CT8 are electrically connected in parallel at both ends of resistor RT8, and the other ends of capacitor CT8 and capacitor CT7 are respectively connected to GND.

[0017] In order to achieve control, the common terminal of capacitor CT7 and capacitor CT8 is electrically connected to one end of diode DT1, and the other end of diode DT1 is connected to power point DVDD, and Power_UpDown_Test voltage detection signal is output through capacitor CT8.

[0018] In summary, compared with the prior art, the utility model has an external AC voltage UN-UL input of 220V, and outputs a voltage value of SPS+18V after passing through the switching power supply AC-DC. The voltage of SPS+18V enters the IO port of the detection terminal Power_UpDown_Test after being divided by a resistor; when the external AC power drops, the output voltage SPS+18V also changes accordingly. The IO of the MCU system has a threshold voltage of 1.4V. When the MCU system detection voltage reaches above 1.4V, the system works normally. When the detection pin voltage of the IO port is lower than 1.4V, the MCU system enters a low power consumption mode. The working flow diagram of the system circuit is shown in the attached figure. Figure 2 When the external input voltage of this circuit is very high, the IO port of the detection pin Power_UpDown_Test is within the voltage range it can withstand: it has a simple structure, low production cost, short design cycle, high versatility, environmentally friendly use, and is suitable for MCUs with different thresholds. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a circuit diagram of the utility model.

[0020] Figure 2 It is a schematic diagram of the circuit of power on and off of the utility model.

[0021] Figure 3 This is a power-on detection flow chart of the utility model.

[0022] Figure 4 This is a power-off detection flow chart of the utility model.

[0023] Figure 5 It is a power supply voltage block diagram of the utility model.

[0024] in:

[0025] RT6, RT7, RT8 are chip resistors used for voltage division

[0026] CT7, CT8, CN26, CN30, CN32, CN28, CN31 are chip ceramic capacitors used to filter out interference signals.

[0027] DT1 is a SMD Schottky diode

[0028] DN15 and DN16 are SMD rectifier diodes used for rectification and voltage backflow prevention.

[0029] EN9 is a plug-in aluminum electrolytic capacitor used for filtering and energy storage

[0030] LN5 is a plug-in industrial mode inductor, used to suppress the influence of industrial mode interference signals on the power supply.

[0031] Resistor RN34, diode DN15, capacitors CN26 and CN30 form an RC loop to absorb the peak voltage of the switching power supply. When laying out, try to keep the loop as small as possible.

[0032] Power_UpDown_Test is a voltage detection signal, which is connected to the MCU end for voltage detection. DETAILED DESCRIPTION

[0033] A diode-based system protection circuit of this embodiment, such as Figure 1-5 As shown in the figure, the diode-based system protection circuit (attached Figure 1) includes diodes DT1, DN15, DN16, resistors RT6, RT7, RT8, RN34, RN38, RN43, capacitors CT7, CT8, CN26, CN30, CN32, CN28, CN31, and aluminum electrolytic capacitor EN9; among them, the auxiliary end SPSO of the AC-DC switching power supply transformer absorbs the peak voltage value of the circuit through the RC circuit composed of resistor RN34, capacitors CN26, CN30, CN32, and rectifier diode DN15, and then a power-mode inductor LN5 is connected in parallel at both ends of capacitor CN32. The main function of the power-mode inductor LN5 is to suppress electromagnetic interference and improve signal quality. Capacitors CN28 and CN31 are connected in parallel at both ends of the power-mode inductor LN5 for filtering and energy storage. The voltage of SPS+18V must be rectified by a rectifier diode DN16. In addition, the rectifier diode DN16 has a function to prevent voltage backflow. The voltage connection point of SPS+18V is connected to one end of resistor RT6, the other end of resistor RT6 is connected in series with resistor RT7, the other end of resistor RT7 is connected to one end of resistor RT8, the other end of resistor RT8 is connected to GND, one end of resistor RT8 is connected to one end of capacitor CT7, capacitor CT7 and capacitor CT8 are connected in parallel on one side of resistor RT8, capacitor CT8 and the other end of capacitor CT7 are connected to GND, one end of diode DT1 is connected to the common non-ground end of capacitor CT7 and capacitor CT8, the other end of diode DT1 is connected to the power point DVDD, and the Power_UpDown_Test voltage detection signal is output through capacitor CT8.

[0034] It is obvious for those skilled in the art to combine multiple technical solutions of the present invention, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0035] In the process of developing and designing smart meters, there are many power supply design schemes, such as BUCK power supply, BOOST power supply, RC power supply, switching power supply, etc. If the design uses a switching power supply, it is necessary to test the cross-regulation rate of the switching power supply. When the back-end load is very high, the voltage change of the front-end of the switching power supply will be relatively large. The safety of the system needs to consider many factors. Resistors RT6, RT7, and RT8 are voltage-dividing resistors. When the cross-regulation rate voltage at SPS+18V output by the switching power supply AC-DC is relatively high, the voltage divided by resistor RT8 is relatively large, and the voltage of the Power_UpDown_Test voltage detection pin may exceed the threshold of the MCU system, causing the MCU to fail and the smart meter will not work properly. The role of DT1 is a voltage-embedded diode. When the voltage value obtained by the resistor voltage divider exceeds the threshold of the MCU system, the diode DT1 will play an embedded role, preventing the voltage value of the detection pin from exceeding the voltage at DVDD, which fully utilizes the single-phase conductivity of the diode. Capacitors CT7 and CT8 are filter capacitors that filter the Power_UpDown_Test signal to prevent false detection of power on and off. The following formula is the formula for the voltage of the power on and off detection pin:

[0036]

[0037] The voltage value at the detection pin is obtained by resistor voltage division. The selection of resistors RT6, RT7, and RT8 is based on the threshold voltage of the MCU system. When selecting the resistance value, the maximum value of the output voltage under the maximum voltage condition should be fully considered to see if it exceeds the maximum value of the MCU system; there is another situation. When the switching power supply is AC-DC, the impact of the voltage change caused by the cross-regulation rate of the switching power supply on the MCU system should be considered.

Claims

1. A diode-based system protection circuit, characterized in that: Including RC circuit, diode DN16, capacitors CN28, CN31, aluminum electrolytic capacitor EN9; The RC loop is electrically connected with an industrial mode inductor LN5; Capacitors CN28 and CN31 are connected in parallel at both ends of the industrial mode inductor LN5; Connect SPS+18V to the input terminals of capacitors CN28 and CN31; SPS+18V is also connected to voltage MHVDD through diode DN16.

2. The diode-based system protection circuit according to claim 1, characterized in that: The RC circuit includes resistor RN34, capacitors CN26, CN30, CN32, and rectifier diode DN15; One end of the resistor RN34 is used to connect to the auxiliary terminal SPSO of the AC-DC switching power supply transformer; the other end of the resistor RN34 is connected to the ground through the capacitor CN26 and then through the parallel capacitors CN30 and CN32. The series resistor RN34, capacitor CN26 and rectifier diode DN15 are connected in parallel.

3. A diode-based system protection circuit according to claim 2, characterized in that: A resistor RN38 is connected next to the industrial mode inductor LN5.

4. The diode-based system protection circuit according to claim 3, characterized in that: Connect the power mode inductor LN5 in parallel across the capacitor CN32.

5. The diode-based system protection circuit according to claim 3, characterized in that: The voltage connection point of SPS+18V is electrically connected to resistors RT6 and RT7 in series, the other end of resistor RT7 is electrically connected to one end of resistor RT8, the other end of resistor RT8 is connected to GND, and one end of resistor RT8 is electrically connected to one end of capacitor CT7; capacitors CT7 and CT8 are electrically connected in parallel at both ends of resistor RT8, and the other ends of capacitor CT8 and capacitor CT7 are respectively connected to GND.

6. The diode-based system protection circuit according to claim 3, characterized in that: The common non-ground terminal of the capacitor CT7 and the capacitor CT8 is electrically connected to one end of the diode DT1 , and the other end of the diode DT1 is connected to the power point DVDD, and the Power_UpDown_Test voltage detection signal is output through the capacitor CT8 .

7. The diode-based system protection circuit according to claim 3, characterized in that: Resistors RT6, RT7, and RT8 are voltage-dividing resistors.

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