阅读说明：本技术 一种新型微型电子空气开关 (Novel miniature electronic air switch ) 是由 赵忠彪 夏政伟 李娜 刘科 于 2020-12-07 设计创作，主要内容包括：本发明公开了一种新型微型电子空气开关,包括与交流电连接的总开关保护电路、与总开关保护电路连接的若干支路保护电路,支路保护电路与相应的供电设备连接,电压采用过压欠压保护,电路简单,可扩展性好,重量轻,它不仅具有漏电保护、过压保护、过流保护等功能,还自带LCD液晶显示屏,可实时显示用户电压、电流、功率,还具有支路故障显示,故障自恢复功能,用户操作界面友好,不仅实用而且美观,而且保护更加准确、设备更加智能化。(The invention discloses a novel miniature electronic air switch, which comprises a main switch protection circuit connected with alternating current and a plurality of branch circuit protection circuits connected with the main switch protection circuit, wherein the branch circuit protection circuits are connected with corresponding power supply equipment, the voltage adopts overvoltage and undervoltage protection, the circuit is simple, the expandability is good, the weight is light, the miniature electronic air switch not only has the functions of leakage protection, overvoltage protection, overcurrent protection and the like, but also is provided with an LCD (liquid crystal display) screen, can display the voltage, the current and the power of a user in real time, and also has the functions of branch circuit fault display and fault self-recovery, the user operation interface is friendly, the miniature electronic air switch is practical and attractive, the protection is more accurate, and the equipment is.)

1. A novel miniature electronic air switch is characterized in that: the automatic control system comprises a main switch protection circuit connected with alternating current, a plurality of branch protection circuits connected with the main switch protection circuit, wherein the branch protection circuits are connected with corresponding electric equipment, the main switch protection circuit comprises a controller CPU, a voltage measurement circuit electrically connected with the controller CPU, an AD sampling reference source circuit electrically connected with the controller CPU, a key circuit electrically connected with the controller CPU, an LCD display module electrically connected with the controller CPU, an electric leakage detection circuit electrically connected with the controller CPU, a total current sampling control protection circuit electrically connected with the controller CPU, a branch current sampling control protection circuit electrically connected with the controller CPU, an isolation power supply module electrically connected with the controller CPU, and a fault processing logic gate circuit electrically connected with the controller CPU, and the controller CPU is electrically connected with each branch protection circuit.

2. The novel miniature electronic air switch of claim 1, wherein: the isolation power supply module comprises a bridge stack U25 connected with alternating current AC1 and alternating current AC2, an inductor L3 connected with the output end of the bridge stack U25 and used for filtering current noise, a filter capacitor C26 connected with the other end of the inductor L3 and a bridge stack U25, a filter capacitor C27, a filter capacitor C18, a filter capacitor C12 and a filter capacitor C14, wherein two ends of the filter capacitor C14 are electrically connected with a power supply chip U15, the power supply chip U15 is connected with a power supply VCC5 through an inductor L4, an inductor L5, a capacitor C15, a capacitor C29, a capacitor C13 and a capacitor C28, and the alternating current AC1 and the alternating current AC2 are connected with a power supply VCC12 through an inductor L3, a filter capacitor C26, a filter capacitor C27, a filter capacitor C18, a filter capacitor C12 and a filter capacitor C14.

3. The novel miniature electronic air switch of claim 1, wherein: the leakage protection circuit comprises a photoelectric coupler U16, and an adjusting resistor R23 and a resistor R23 which are respectively electrically connected with the photoelectric coupler U16, and the size of leakage protection current is adjusted by adjusting the size of R23.

4. The novel miniature electronic air switch of claim 1, wherein: the voltage measuring circuit comprises a linear optocoupler U17, a resistor R25, a protection diode D6, a filter capacitor C19 and a resistor R26, wherein the resistor R25 is electrically connected with the linear optocoupler U17.

5. The novel miniature electronic air switch of claim 1, wherein: the total current sampling control protection circuit comprises an MOSFET switching tube U20, an MOSFET switching tube U21, a floating drive chip U19 electrically connected with the MOSFET switching tube U20 and the MOSFET switching tube U21, a low-noise operational amplifier U18B, a protection voltage stabilizing diode Z2 connected with the non-inverting input end of U18B, an adjustable potentiometer VR6 and a protection resistor R32 connected with the adjustable potentiometer, a temperature compensation resistor RT2 connected with the inverting input end of the low-noise operational amplifier U18B, a gain adjustment potentiometer VR5 and a resistor R36 connected with the temperature compensation resistor RT2, a filter capacitor C24, a low-noise operational amplifier U18 output voltage is divided by an isolation resistor R34 and a filter capacitor C25, a controller CPU ADC is then sent to carry out total protection current sampling, and is sent to the inverting input end of a comparator U18A after being divided by a voltage dividing resistor R35 and a protection threshold adjustment potentiometer VR4, the non-inverting input end of the comparator U18 voltage dividing resistor R36A is connected with the non-inverting input end of the voltage dividing resistor R28, and the protection resistor R30 is used for, the resistor R27 is a current-limiting resistor of the fault indicator lamp D7, and the output of the comparator U18A is connected with the current resistor R31 and the isolation diode D8 and is sent to the IO port of the controller CPU and simultaneously sent to the control end of the MOSFET floating drive chip U19.

6. The novel miniature electronic air switch of claim 1, wherein: the logic gate circuit comprises a three-input AND gate circuit U7, a three-input AND gate circuit U8, a three-input AND gate circuit U10 and a three-input AND gate circuit U12, wherein a pin 1A and a pin 1B of the three-input AND gate circuit U7 are respectively connected with an overcurrent protection signal abnormal pin BH0 of a main circuit and are simultaneously connected with a pin of a CPU and a leakage protection pin LD1, a pin 1C of the three-input AND gate circuit U7 is connected with an interrupt pin INT0 of the controller CPU, pins BH1 and BH20 are respectively branch current protection signal abnormal pins, pins BH1 and BH20 are simultaneously and respectively connected with a control pin of the controller CPU, and events caused by abnormality of the pins BH1 and BH20 are connected with an interrupt pin INT1 of the controller CPU after passing through a three-input AND gate circuit U7, a three-input AND gate circuit U8, a three-input AND gate circuit U10 and a three-input AND gate circuit U12.

7. The novel miniature electronic air switch of claim 1, wherein: the AD sampling reference source circuit comprises a current-limiting resistor R13 connected with a power supply voltage VCC5, a reference source chip TL 431Q 1 connected with a current-limiting resistor R13, a filter capacitor C10 connected with a second pin of the reference source chip TL 431Q 1, a filter capacitor C9, a filter inductor L1, a filter inductor L2 and a filter capacitor C11.

8. The novel miniature electronic air switch of claim 1, wherein: the branch current sampling control protection circuit comprises an MOSFET switching tube U3, an MOSFET switching tube U4, a floating drive chip U2 electrically connected with the MOSFET switching tube U3 and the MOSFET switching tube U4, a low-noise operational amplifier U1A, a protection voltage stabilizing diode Z1 connected with the same-phase input end of U1A, an adjustable potentiometer VR1 and a protection resistor R6 connected with the adjustable potentiometer, a temperature compensation resistor RT1 connected with the reverse-phase input end of a low-noise operational amplifier U1A, a gain adjustment potentiometer VR3 and a resistor R10 connected with the temperature compensation resistor RT1, a filter capacitor C7, a low-noise operational amplifier U1A output voltage is divided by an isolation resistor R8 and a filter capacitor C8, then the branch protection current sampling is sent to an ADC of a controller CPU, and the branch protection current is sent to the reverse-phase input end of a comparator U1B through an isolation diode D4 after being divided by a voltage divider resistor R8 and a protection threshold adjustment potentiometer VR2, the same-phase input end of the comparator U1 is connected with a voltage dividing resistor R87458, and the protection resistor R87458, the resistor R1 is a current-limiting resistor of the fault indicator lamp D1, and the output of the comparator U1B is connected with the current resistor R5 and the isolation diode D2 and is sent to the IO port of the controller CPU and simultaneously sent to the control end of the MOSFET floating drive chip U2.

Technical Field

The invention relates to a household appliance protection device, in particular to a novel miniature electronic air switch.

Background

The invention of the air switch has a long history, has been widely applied from the invention to the present, is the first choice of household and factory power consumption protection, plays an extremely important role, and has obvious advantages. However, as the times develop, people can not ignore and tolerate the open defects more and more, which mainly includes the following aspects: (1) the protection function is single, and the protection is mainly embodied in leakage protection and overcurrent protection; (2) the protection accuracy is poor. For example, the 60A idle switch has a large error in protection current when the switch is turned off; (3) the air switch contact is made of red copper, brass or alloy materials and is a non-renewable material, the copper reserves in China are low, and a large amount of foreign exchange has to be spent and imported from foreign countries; (4) is heavy. Great inconvenience is brought to installation and maintenance of workers, and particularly, the switch of the weak girl is laborious; (5) the lifetime is relatively short. For equipment such as a machine room which is frequently switched on and switched off, the manual switching-on times are more, and the contact is frequently subjected to circuit failure caused by ignition and ablation. With the rapid development of electronic technology in the times, especially the rapid development of power switching device technology and the demand of people for information and digital devices, people need a novel household electronic air switch/circuit breaker to replace the traditional devices.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a novel miniature electronic air switch which is simple in structure and convenient to use.

The purpose of the invention is realized as follows:

a novel miniature electronic air switch is characterized in that: the automatic control system comprises a main switch protection circuit connected with alternating current, a plurality of branch protection circuits connected with the main switch protection circuit, wherein the branch protection circuits are connected with corresponding electric equipment, the main switch protection circuit comprises a controller CPU, a voltage measurement circuit electrically connected with the controller CPU, an AD sampling reference source circuit electrically connected with the controller CPU, a key circuit electrically connected with the controller CPU, an LCD display module electrically connected with the controller CPU, an electric leakage detection circuit electrically connected with the controller CPU, a total current sampling control protection circuit electrically connected with the controller CPU, a branch current sampling control protection circuit electrically connected with the controller CPU, an isolation power supply module electrically connected with the controller CPU, and a fault processing logic gate circuit electrically connected with the controller CPU, and the controller CPU is electrically connected with each branch protection circuit.

The isolation power supply module comprises a bridge stack U25 connected with alternating current AC1 and alternating current AC2, an inductor L3 connected with the output end of the bridge stack U25 and used for filtering current noise, a filter capacitor C26 connected with the other end of the inductor L3 and a bridge stack U25, a filter capacitor C27, a filter capacitor C18, a filter capacitor C12 and a filter capacitor C14, wherein two ends of the filter capacitor C14 are electrically connected with a power supply chip U15, the power supply chip U15 is connected with a power supply VCC5 through an inductor L4, an inductor L5, a capacitor C15, a capacitor C29, a capacitor C13 and a capacitor C28, and the alternating current AC1 and the alternating current AC2 are connected with a power supply VCC12 through an inductor L3, a filter capacitor C26, a filter capacitor C27, a filter capacitor C18, a filter capacitor C12 and a filter capacitor C14.

The leakage protection circuit comprises a photoelectric coupler U16, and an adjusting resistor R23 and a resistor R23 which are respectively electrically connected with the photoelectric coupler U16, and the size of leakage protection current is adjusted by adjusting the size of R23.

The voltage measuring circuit comprises a linear optocoupler U17, a resistor R25, a protection diode D6, a filter capacitor C19 and a resistor R26, wherein the resistor R25 is electrically connected with the linear optocoupler U17.

The total current sampling control protection circuit comprises an MOSFET switching tube U20, an MOSFET switching tube U21, a floating drive chip U19 electrically connected with the MOSFET switching tube U20 and the MOSFET switching tube U21, a low-noise operational amplifier U18B, a protection voltage stabilizing diode Z2 connected with the non-inverting input end of U18B, an adjustable potentiometer VR6 and a protection resistor R32 connected with the adjustable potentiometer, a temperature compensation resistor RT2 connected with the inverting input end of the low-noise operational amplifier U18B, a gain adjustment potentiometer VR5 and a resistor R36 connected with the temperature compensation resistor RT2, a filter capacitor C24, a low-noise operational amplifier U18 output voltage is divided by an isolation resistor R34 and a filter capacitor C25, a controller CPU ADC is then sent to carry out total protection current sampling, and is sent to the inverting input end of a comparator U18A after being divided by a voltage dividing resistor R35 and a protection threshold adjustment potentiometer VR4, the non-inverting input end of the comparator U18 voltage dividing resistor R36A is connected with the inverting input end of the voltage dividing resistor R3687458, and the protection threshold adjustment resistor R72 is used, r27 is the current-limiting resistor of fault indicator lamp D7, and the output of comparator U18A is connected current resistor R31 and isolation diode D8 and is sent to the control end of MOSFET tube floating drive chip U19 simultaneously when the IO mouth of controller CPU is sent.

The logic gate circuit comprises a three-input AND gate circuit U7, a three-input AND gate circuit U8 and a three-input AND gate

The three-input AND gate circuit U10, the three-input AND gate circuit U12, a pin 1A and a pin 1B of a three-input AND gate circuit U7 are respectively connected with an overcurrent protection signal abnormal pin BH0 of a main circuit and are simultaneously connected with a pin of a CPU and a leakage protection pin LD1, a pin 1C of a three-input AND gate circuit U7 is connected with an interrupt pin INT0 of a controller CPU, pins BH1 and BH20 are respectively branch current protection signal abnormal pins, pins BH1 and BH20 are simultaneously and respectively connected with a control pin of the controller CPU, and events caused by abnormality of the pins BH1 and BH20 pass through a three-input AND gate circuit U7, a three-input AND gate circuit U8, a three-input AND gate circuit U10 and a three-input AND gate circuit U12 logic gate chip and then are connected with the controller CPU interrupt pin INT 1.

The AD sampling reference source circuit comprises a current-limiting resistor R13 connected with a power supply voltage VCC5, a reference source chip TL 431Q 1 connected with a current-limiting resistor R13, a filter capacitor C10 connected with a second pin of the reference source chip TL 431Q 1, a filter capacitor C9, a filter inductor L1, a filter inductor L2 and a filter capacitor C11.

The branch current sampling control protection circuit comprises an MOSFET switching tube U3, an MOSFET switching tube U4, a floating drive chip U2 electrically connected with the MOSFET switching tube U3 and the MOSFET switching tube U4, a low-noise operational amplifier U1A, a protection voltage stabilizing diode Z1 connected with the same-phase input end of U1A, an adjustable potentiometer VR1 and a protection resistor R6 connected with the adjustable potentiometer, a temperature compensation resistor RT1 connected with the reverse-phase input end of a low-noise operational amplifier U1A, a gain adjustment potentiometer VR3 and a resistor R10 connected with the temperature compensation resistor RT1, a filter capacitor C7, a low-noise operational amplifier U1 28 output, an isolation resistor R8, a filter capacitor C8, a controller CPU ADC for branch protection current sampling, a voltage division by a voltage dividing resistor R8 and a protection threshold adjustment potentiometer VR2, a reverse-phase input end of a comparator U1B, a same-phase input end of the comparator U1B is connected with a voltage dividing resistor R2, and a protection threshold adjustment resistor R8672 is used for adjusting the current (required for adjusting the threshold value of the protection threshold) (, r1 is the current limiting resistor of fault indicator lamp D1, and the output of comparator U1B is connected current resistor R5 and isolation diode D2 and is sent to the control end of MOSFET tube floating drive chip U2 simultaneously when the IO mouth of controller CPU.

The invention has the beneficial effects that: the invention adopts overvoltage and undervoltage protection for voltage, has simple circuit, good expandability and light weight, not only has the functions of leakage protection, overvoltage protection, overcurrent protection and the like, but also has an LCD (liquid crystal display) screen, can display the voltage, the current and the power of a user in real time, also has the functions of branch fault display and fault self-recovery, is friendly in user operation interface, is not only practical and beautiful, but also has more accurate protection and more intelligent equipment.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic diagram of a main switch protection circuit according to the present invention;

FIG. 3 is a circuit diagram of an isolated power supply module according to the present invention;

FIG. 4 is a circuit diagram of the leakage protection circuit of the present invention;

FIG. 5 is a circuit diagram of a voltage measurement circuit according to the present invention;

FIG. 6 is a circuit diagram of the total current sampling control protection circuit of the present invention;

FIG. 7 is a circuit diagram of a fault handling logic gate circuit of the present invention;

FIG. 8 is a circuit diagram of the controller CPU master control circuit of the present invention;

FIG. 9 is a circuit diagram of an AD sampling reference source circuit of the present invention;

FIG. 10 is a circuit diagram of an analog channel expansion of the present invention;

FIG. 11 is a circuit diagram of the current sampling signal input interface of each branch according to the present invention;

FIG. 12 is a circuit diagram of the key of the present invention;

FIG. 13 is a circuit diagram of an LCD display module according to the present invention;

FIG. 14 is a truth table for LCD display according to the present invention;

FIG. 15 is a circuit diagram of a branch current sampling control protection circuit according to the present invention.

Detailed Description

The invention is further illustrated by the following figures and examples.

Example 1:

as shown in figures 1 and 2, a novel miniature electronic air switch comprises a main switch protection circuit connected with alternating current, a plurality of branch protection circuits connected with the main switch protection circuit, wherein the branch protection circuits are connected with corresponding power supply equipment, the main switch protection circuit comprises a controller CPU, a voltage measurement circuit electrically connected with the controller CPU, an AD sampling reference source circuit electrically connected with the controller CPU, a key circuit electrically connected with the controller CPU, an LCD display module electrically connected with the controller CPU, an electric leakage detection circuit electrically connected with the controller CPU, a total current sampling control protection circuit electrically connected with the controller CPU, a branch current sampling control protection circuit electrically connected with the controller CPU, an isolation power supply module electrically connected with the controller CPU, and a fault processing logic gate circuit electrically connected with the controller CPU, the controller CPU is electrically connected with each branch circuit protection circuit, the structure diagram of the main switch protection circuit is shown in figure 2, and when the controller CPU samples the leakage behavior between the AC motor shells (the ground), the main switch protection circuit cuts off the main switch, thereby playing the role of protecting operators or each branch circuit electric equipment. The CPU samples AC input voltage, and the main switch protection circuit cuts off the main switch if detecting that the AC has overvoltage or undervoltage behavior, thereby playing a role in protecting each branch of electric equipment. The main protection switch circuit can independently set the current required to be protected of each branch circuit and the total current of the circuit required to be protected through the key circuit, sample the current of each branch circuit and simultaneously carry out corresponding switch control on each branch circuit power device. The isolation power supply module provides working voltage for the main protection switch circuit and each branch protection switch circuit. The LCD display module displays various information on the operation of the circuit, such as voltage, total current, branch current, etc. The fault processing logic gate circuit carries out logic and INT0 (external interrupt 0) of the back-feeding controller CPU on the earth leakage protection signal and the total branch overcurrent protection signal, carries out logic and INT1 (external interrupt 1) of the back-feeding controller CPU on the overcurrent protection signal generated by each branch, and immediately closes a corresponding power device after the controller CPU receives the interrupt signal, so that hiccup phenomenon of the circuit is avoided on one hand, and electric equipment of each branch is protected on the other hand. The AD sampling reference source circuit provides a reliable measurement reference for the AD sampling of the CPU. The branch circuit protection switch circuit completes functions of branch circuit current differential sampling measurement, branch circuit current overcurrent protection and the like, can be freely expanded according to user requirements, and has 19 maximum expansion modules at present.

As shown in fig. 3, the isolation power supply module includes a bridge stack U1 connected to an alternating current AC1 and the alternating current AC1, an inductor L1 connected to an output end of the bridge stack U1 and used for filtering current noise, a filter capacitor C1 connected to the other end of the inductor L1 and the bridge stack U1, the filter capacitor C1 and the filter capacitor C1, two ends of the filter capacitor C1 are electrically connected to the power supply chip U1, the power supply chip U1 is filtered by the inductor L1, the capacitor C1 and the power supply VCC1, the alternating current AC1 and the alternating current AC1 are filtered by the inductor L1, the filter capacitor C1 and the filter capacitor C1 are connected to a sampling resistor V3612 after passing through the isolation transformer, so as to measure a current difference of the secondary side of the MOSFET 1, therefore, weak current power supply needs to be isolated and powered, the U25 is a bridge stack, 12V alternating current on the secondary side of an isolation transformer is rectified into steamed bread waves in a full-wave mode, current noise is filtered through an inductor L3, voltage filtering is carried out through a filter capacitor C26, a filter capacitor C27, a filter capacitor C18, a filter capacitor C12 and a filter capacitor C14 to obtain VCC12, then the VCC5 which is low in voltage noise and clean in current noise and is needed by a controller CPU and a low-noise operational amplifier is obtained after the VCC5 is sent to a linear power supply chip U15 and passes through a pi-type filter network formed by an inductor L4, an inductor L5, a capacitor C15, a capacitor C29, a capacitor C13 and a capacitor C28.

As shown in fig. 4, the leakage protection circuit includes a photocoupler U16, and an adjusting resistor R23 and a resistor R23 electrically connected to the photocoupler U16, respectively, and adjusts the magnitude of the leakage protection current by adjusting the magnitude of R23, and the specific operation principle is as follows: when the leakage phenomenon exists between the live wire L of the alternating current and the chassis ground, the light emitting diode of the photoelectric coupler U16 is conducted, so that the pin LD1 outputs a low level, otherwise, the pin LD1 outputs a high level, and the CPU of the controller can judge whether a leakage accident occurs by detecting the signal, so that the leakage protection is realized.

As shown in fig. 5, the voltage measurement circuit includes a linear optocoupler U17, a current limiting resistor R25, a protection diode D6, a filter capacitor C19, and a resistor R26, which are electrically connected to the linear optocoupler U17, respectively, and the user voltage sampling realizes the isolation of strong current and weak current through the linear optocoupler U17. The specific work is as follows: the positive half-period alternating current of the alternating current flows through a current limiting resistor R25, a voltage which has a linear relation with the alternating current is obtained on a 3-pin resistor R26 and a filter capacitor C19 of a linear optocoupler behind a light emitting diode of a linear optocoupler U17, the voltage is sent to an ADC0 pin of a controller CPU for sampling, and then the alternating current input voltage can be measured, in order to reduce the power consumption of the controller CPU, the pin is simultaneously connected with a comparator of the controller CPU for zero-crossing comparison, when the alternating current has a zero-crossing event, the controller CPU is started for AD sampling, sampling data are sequenced from small to large, and the effective value of the alternating current is the sampling maximum Umax & ltu &Thus, the input voltage is obtained, and the current returns to L after passing through a current limiting resistor R25 of a protective diode D6 at the N end in the negative half period of the alternating current. The user can set the highest voltage and the lowest voltage of protection through the key circuit, and the circuit cuts off the power supply when the external power supply is higher than or lower than the set value, thereby realizing overvoltage or undervoltage protection.

As shown in FIG. 6, the total current sampling control protection circuit includes a MOSFET switch tube U20, a MOSFET switch tube U21, a floating driver chip U19 electrically connected to the MOSFET switch tube U20 and the MOSFET switch tube U21, a low noise operational amplifier U18B, a protection zener diode Z2 connected to the non-inverting input terminal of U18B, an adjustable potentiometer VR6 and a protection resistor R32 connected to the adjustable potentiometer, a temperature compensation resistor RT2 connected to the inverting input terminal of the low noise operational amplifier U18B, a gain adjustment potentiometer VR5 and a resistor R36 connected to the temperature compensation resistor RT2, a filter capacitor C24, a low noise operational amplifier U18B output via an isolation resistor R34, a filter capacitor C25, a CPU ADC for total protection current sampling, a voltage divider resistor R35 and a protection threshold adjustment potentiometer VR4 for outputting a voltage divider diode D10 to the inverting input terminal of a comparator U18A, a voltage divider resistor R28 connected to the non-inverting input terminal of the comparator U18R 18A, and a resistor R30 for adjusting the protection current (protection threshold) (for adjusting the protection current), the resistor R27 is a current-limiting resistor of the fault indicator lamp D7, and the output of the comparator U18A is connected with the current resistor R31 and the isolation diode D8 and is sent to the control end of the MOSFET floating drive chip U19 while being sent to the CPU IO port.

The main circuit of the total current sampling control protection circuit is connected with a main control loop through an N-channel MOSFET switch tube U20 and an N-channel MOSFET switch tube U21 back to back, the MOSFET switch tube U20 and the MOSFET switch tube U21 are controlled by a floating drive chip U19 in an on-off mode, and the total current measuring sampling resistor takes on-state resistors of the N-channel MOSFET switch tube U20 and the N-channel MOSFET switch tube U21 as sampling resistors to realize differential measurement of current.

The specific work is as follows: when ac current flows from L to L1 through N-channel MOSFET switch U20 and N-channel MOSFET switch U21, the non-inverting and inverting terminals of the low noise operational amplifier U18B generate voltages (U18BP-U18BN) with magnitude of Iz RU21+ U20t, i.e., U18BP-U18BN = Iz RU21+ U20t, where RU21 is the on-state resistance of the switch U21, U20t is the body diode voltage of the switch U20 (approximately a constant around 0.2V), the output voltage U18Bout of the integrated operational amplifier U18B is (Iz RU21+ U20 t) (RT 2+ VR 5)/R36, where (RT 2+ VR 5)/R36 = R32/VR 6), and VR5 is used to adjust the gain of the VR circuit.

Because the MOSFET has a positive temperature coefficient, in order to ensure the accuracy of a measurement result, the RT2 adopts a compensation resistor with the positive temperature coefficient, and the U18Bout is sent to an AD sampler of the CPU to sample the total circuit working current after passing through an isolation resistor R34 and a filter capacitor C25. In order to improve the fast response of the module and prevent the N-channel MOSFET switch tube U20 from being burnt out when the N-channel MOSFET switch tube U21 exceeds the maximum operating current, the output voltage U18Bout of the operational amplifier U18B is divided by the resistor R35 and the adjustable potentiometer VR4 and then is fed to the inverting input terminal of the comparator U18A through the isolating diode D10, the output voltage U18out of the operational amplifier U18B is also fed to the inverting input terminal of the comparator U18A through the isolating resistors R34 and R33 and then is added, the adjustable potentiometer VR4 can adjust the circuit to protect the maximum current, and the VCC5 is divided by the voltage dividing resistors R28 and R30 and then is fed to the non-inverting input terminal of the comparator U18A (the comparator threshold voltage U18A). When the current passing through the N-channel MOSFET switch tube U20 and the N-channel MOSFET switch tube U21 is larger than a protection value, the comparator U18A outputs a low level, the low level is sent to the single chip microcomputer through the resistor R31 and the isolating diode D8, and the control end 2 of the MOSFET driving chip U19 is blocked at the same time, so that the power supply of the main circuit is cut off, due to the rapid characteristic of the comparator, the rapid protection of the circuit is realized, the D7 is a fault indicator lamp, and the indicator lamp is turned on when an overcurrent event occurs.

When the N-channel MOSFET switch tube U20 and the N-channel MOSFET switch tube U21 are turned off, U18P-U18N =220V ac, in order to protect the integrated operational amplifier U18B, R32 is a current-limiting resistor, and Z2 is a protection zener diode, then U18BP-U18BN = UZ (the zener value of the protection zener diode). Once the circuit enters the protection state, the main circuit power supply is cut off, I_z=0，U20t=0，U18Bout=（I_z*R_U21+ U20 t) ((RT 2+ VR 5)/R36), so that the output voltage U18Bout of the operational amplifier U18B is U18Bout = 0; the circuit can switch on again, and hiccup phenomenon can appear in the repetitive circuit in proper order, and for avoiding appearing this type of condition, BH0 connects controller CPU's IO mouth, and in case controller CPU detects that the circuit appears overflowing linearity, controller CPU's IO mouth output low level BH0 promptly is the low level to thoroughly block N channel MOSFET switch tube U20, N channel MOSFET switch tube U21's driver chip U19, thereby realize the permanent cut-off of circuit. In order to increase the adaptability of the circuit and reduce the on-state resistance, one or more groups of MOSFET tubes can be connected in parallel to the N-channel MOSFET switching tube U20 and the N-channel MOSFET switching tube U21. To improve the controllerThe CPU has quick response to faults, and abnormal signals of the main circuit and each branch circuit are processed by the logic gate circuit and then sent to an interrupt pin of the CPU of the controller.

As shown in FIG. 7, the logic gate circuit comprises a three-input AND gate circuit U7, a three-input AND gate circuit U8, a three-input AND gate circuit U10 and a three-input AND gate circuit U12, wherein a pin 1A of a three-input AND gate circuit U7 is connected with an overcurrent protection signal abnormal pin BH0 of a main circuit and is simultaneously connected with a pin of a CPU, a pin 1B is respectively connected with a leakage protection pin LD1 and is also connected with a pin of the CPU, a pin 1C of the three-input AND gate circuit U7 is connected with an interrupt pin 0 of the controller CPU, pins BH1 to BH20 are respectively branch current protection signal abnormal pins, pins BH1 to BH20 are respectively connected with a control pin of the controller CPU, events caused by abnormality of pins BH1 to BH20 are respectively connected with an interrupt pin 1 of the controller CPU after a logic gate chip through the three-input AND gate circuit U7, the three-input AND gate circuit U8, the three-input AND gate circuit U10 and the three-input AND gate circuit U12 are respectively connected with the overcurrent protection signal abnormal pin 1A of the main circuit U3745 and the overcurrent A pin BH0 is connected to a pin of a controller CPU and a leakage protection pin LD1 is also connected to a pin of the controller CPU, a pin 1C of a three-input AND gate circuit U7 is connected to an interrupt pin INT0 of the controller CPU, when main circuit current overcurrent or leakage accident occurs, a pin 1C of the three-input AND gate circuit U7 outputs low level to trigger the interrupt of the controller CPU, the controller CPU enables a pin BH0 to output low level to block a control pin 2 of a driving chip U19 to block an N-channel MOSFET switch tube U20 and an N-channel MOSFET switch tube U21, so that the hiccup phenomenon of the circuit is avoided, if the circuit has the leakage accident, a pin LD1 and a pin 1C of the three-input AND gate circuit U7 output low level to trigger the interrupt of the controller CPU, the controller CPU enables a pin BH0 to output low level to block a control pin 2 of the driving chip U19, so that the N-channel MOSFET switch tube U20 and the leakage protection tube LD1 output low level, And the N-channel MOSFET switching tube U21 drives the chip U19 again until the user eliminates the leakage accident and resets manually, so that the circuit is powered up again, and the leakage protection is realized.

BH1 to BH20 are branch current protection signal abnormality pins, which are connected to the control pin of the controller CPU, respectively, and events caused by their abnormality are connected to the controller CPU interrupt pin INT1 after passing through the three-input and gate circuit U7, the three-input and gate circuit U8, the three-input and gate circuit U10, and the three-input and gate circuit U12 logic gate chip.

As shown in fig. 8, in the main control circuit diagram of the controller CPU, the LCD DATA pin is an LCD segment code liquid crystal DATA input pin, the controlled main circuit and the branch circuit are both ac, and the current and voltage sampling circuits are both half-wave sampling, so the circuit is designed with zero-crossing detection, a zero-crossing signal after the ac zero-crossing is sent to the non-inverting input terminal of the controller CPU comparator, and the power voltage is sent to the inverting input terminal of the controller CPU comparator after being divided by the voltage dividing resistors R12 and R14 to reduce noise interference.

As shown in fig. 9, the AD sampling reference source circuit includes a current limiting resistor R13 connected to a power supply voltage VCC5, a reference source chip TL 431Q 1 connected to a current limiting resistor R13, a capacitor C10 connected to a second pin of the reference source chip TL 431Q 1, a capacitor C9, an inductor L1, an inductor L2, and a capacitor C11.

The power supply voltage VCC5 is sent to the reference source chip Q1 (TL 431) after passing through the current-limiting resistor R13, and the reference voltage obtained by the second pin of the reference source chip Q1 (TL 431) is sent to the external reference signal pin and the analog low pin of the controller CPU after passing through the pi-type filter network formed by the capacitor C10, the capacitor C9, the inductor L1, the inductor L2 and the capacitor C11.

As shown in fig. 10, in the circuit diagram of analog channel expansion, since the number of AD sampling channels of the controller CPU is too small, a U9 analog switch (74 HC 4052) may be used to expand the input channels, and the operation principle thereof is not described herein again.

As shown in fig. 11, the input interface of each branch current sampling signal is schematically illustrated, and the total branch of the protection circuit is 19 branches, which can meet the requirements of most users, for example, 4 bedrooms, kitchen, living room, socket, lighting, water heater, etc. of a general user, and will not be described herein again.

Fig. 12 shows, in the circuit diagram of the key module, the power consumption of the user is abnormal, the user can press the S1 key to realize the manual reset of the fault, or can set the automatic reset through the S3 function key, the automatic reset time is set by the keys S4, S5, and S6, and meanwhile, the protection circuit of the total current and the protection current of each branch are also set through the keys S3, S4, S5, and S6, so as to increase the convenience and flexibility of use, for example, the CPU cuts off the power supply after finding that the power consumption of a certain dormitory is overloaded, delays several minutes and then recovers the power supply again, and the total switch can be cut off or opened through the key S2 during the equipment maintenance.

As shown in fig. 13, in the LCD display module circuit, U13 is an LCD driver chip, LCD DATA is a display DATA input pin, R15 is a segment code driving current adjusting resistor, and P26 is a liquid crystal panel. The display content is voltage 3 bits, main circuit current 2 bits, branch number 1 bits, branch current 2 bits, and power 3 bits.

As shown in fig. 14, the LCD displays a truth table.

As shown in fig. 15, the branch protection switch circuit includes a branch current sampling protection control circuit, where the branch current sampling protection control circuit includes a MOSFET switch tube U3, a MOSFET switch tube U4, a floating driver chip U2 electrically connected to the MOSFET switch tube U3 and the MOSFET switch tube U4, a low noise operational amplifier U1A, an output voltage U1Aout of an operational amplifier U1A, an isolation resistor R8, a filter capacitor C8, an adjustable potentiometer VR2, an isolation diode D4, a comparator U1B, a voltage dividing resistor R2, a voltage dividing resistor R4, a resistor R5, an isolation diode D2, and a fault indicator lamp D1, and each branch is of a modular design, and is free and simple to expand, and only needs to connect several power supply lines and AD sampling lines to the controller CPU.

The protection and control process is as follows:

(1) in order to improve the reliability of the circuit, the main switch protection circuit and the branch switch protection circuit adopt a double-layer protection strategy: the first layer of MOSFET bears the maximum current fast protection, the protection is realized by hardware by a final comparator of a total current sampling control protection circuit and a branch current sampling protection circuit, and once the circuit current reaches or exceeds the maximum current which can be borne by the power tube, the comparator is triggered immediately to block the driving signal of the power tube, so that the fast protection of the circuit is realized; the second layer of users sets current protection, and users can set the protection current of the main switch protection circuit and each branch switch protection circuit through a key circuit, for example, branch 1, the maximum current that the MOSFET tube can bear is 100A, the users set the protection circuit 50A, when the AD sampler finds that the current exceeds the set value of the users, the CPU of the controller directly blocks the control pin of the drive driving chip of the MOSFET tube, thereby cutting off the power supply of the channel, and realizing overcurrent protection.

(2) The control for avoiding the hiccup phenomenon of the circuit is realized: when the circuit current is close to or exceeds the maximum current that the power tube can bear once, the circuit starts a quick response mechanism to block the power tube, and simultaneously sends an interrupt request to the controller CPU, and the controller CPU immediately pulls down the control pin of the power tube drive chip after receiving the interrupt, thereby avoiding the circuit hiccup, simultaneously lightening the fault indicator lamp, and enabling a user to press a manual reset key to restore the circuit to work after removing the fault.

(3) AD sampling control strategy: on the premise of not influencing the performance, in order to reduce the complexity of circuit design and reduce the cost, the circuit integrated operational amplifier uses a single power supply for power supply, a precise detection circuit is omitted, all AD sampling is realized in the positive half period of alternating current, and a CPU (central processing unit) in the negative half period of the alternating current completes the calculation of sampling data. The specific working process is as follows: in the positive half period of the alternating current, a CPU triggers comparison interruption, simultaneously starts voltage sampling and current sampling of a circuit, sorts sampling data in sequence from small to large, and takes the effective value of the alternating current as the maximum sampling value Umax-The current sampling of the branch circuit is obtained through calculation, the CPU of the negative half cycle of the alternating current finishes the comparison of the sampling value and a set value, and the control and display of the switching tube and other operations.

(4) The algorithm of overcurrent misjudgment is realized: if an alternating current motor is connected into the circuit, the starting current of the alternating current motor is 5 to 7 times of the rated current, the starting time is long and generally requires ten seconds, and in order to prevent the motor from being started normally due to misjudgment of a protection circuit, the control strategy is as follows: (a) if the starting current exceeds the maximum current which can be borne by the power tube, the current starts the first layer of MOSFET to bear the maximum current for rapid protection, and the motor cannot be started normally. (b) If the current is less than the maximum current which can be borne by the power tube and is greater than the maximum working current set by a user, the power tube is turned off temporarily, the next period of the alternating current is turned on again to sample the circuit current for the second time, if the current is less than or equal to the first sampling current, the operation is repeated, after 15 seconds, if the current returns to normal, the circuit is turned on, the controller CPU considers that the circuit is the normal start of the motor, if the second sampling current is greater than the first sampling current and is less than the maximum protection circuit, the controller CPU turns off the power tube in the negative half period of the alternating current, the third period of the alternating current is sampled for the third time, and if the sampling current is gradually increased, the controller CPU starts the overcurrent protection and turns off the.

With the rapid development of electronic technology, especially the improvement of power devices such as domestic IGBTs, silicon carbide, silicon controlled rectifiers and the like, the substitute chips of the power devices using the devices to substitute the MOFET tubes of the circuit are also protected.

The invention adopts overvoltage and undervoltage protection for voltage, has simple circuit, good expandability and light weight, not only has the functions of leakage protection, overvoltage protection, overcurrent protection and the like, but also has an LCD (liquid crystal display) screen, can display the voltage, the current and the power of a user in real time, also has the functions of branch fault display and fault self-recovery, is friendly in user operation interface, is not only practical and beautiful, but also has more accurate protection and more intelligent equipment.