CN1674381A - Under-voltage isolating monitoring circuit - Google Patents

Abstract

A voltage undervoltage isolation monitoring circuit, the monitored power supply voltage is added to the voltage sampling terminal of the voltage reference chip through a voltage dividing resistor, and at the same time added to the anode of the isolated optocoupler primary side light-emitting diode through a current-limiting resistor, and the cathode of the light-emitting diode is connected to The voltage reference chip is used to isolate the collector of the secondary side of the optocoupler and connect to the interrupt port of the single-chip microcomputer, and at the same time connect the power supply of the single-chip microcomputer through a resistor. When the monitored power supply voltage is higher than the protection value, the voltage applied to the voltage sampling terminal of the voltage reference chip through voltage division is higher than the internal reference voltage of the chip, the cathode of the voltage reference chip is turned on to the anode, and the primary side diode of the isolated optocoupler is turned on. The collector of the secondary side is low level; once the monitored power supply voltage is lower than the protection value, the collector of the secondary side of the isolated optocoupler jumps to the power supply voltage of the single-chip microcomputer, that is, high level, and the single-chip microcomputer receives the undervoltage signal of the monitored power supply voltage . The invention can make the operation of the single-chip microcomputer free from the influence of high voltage and strong electricity, and ensure the safety and reliability of the monitoring system.

Description

Voltage undervoltage isolation monitoring circuit

technical field

The invention relates to a voltage undervoltage isolation monitoring circuit, which is used to send an alarm signal to a computer or a single-chip microcomputer when the power supply voltage in the circuit is lower than the allowable value required by the normal operation of the equipment, so that the computer or the single-chip microcomputer stops related work to protect the safety of the equipment. It belongs to the technical field of voltage undervoltage protection.

Background technique

In some electronic equipment systems, if the power supply voltage is lower than a certain value, the electronic equipment will fail or even be damaged. Therefore, the power supply voltage of the computer and electronic equipment system should be used for monitoring. When the power supply voltage is lower than the minimum voltage necessary for the electronic equipment system, a monitoring circuit should be provided to send an alarm signal to the computer or single-chip microcomputer, and the computer or single-chip microcomputer will make the electronic equipment system Realize the undervoltage protection function to ensure the safety of the equipment.

Typical examples of such circuits are numerous. Among them, the circuit for monitoring battery voltage undervoltage is to connect the battery voltage and the threshold value of undervoltage protection to the non-inverting terminal and inverting terminal of the comparator respectively. When the battery voltage is lower than the threshold value of undervoltage protection, the output state of the comparator changes, thereby A protection or alarm signal is provided to make the battery exit the power supply state and realize battery undervoltage protection.

However, this circuit example is applied to the voltage monitoring of single-chip microcomputer working in a high-voltage and strong-electricity environment, and there is a threat to the safety of the single-chip microcomputer system by high-voltage and strong electricity, because the equipment under high-voltage and strong electricity will be accompanied by electromagnetic interference during operation. Once the electromagnetic interference invades the single-chip microcomputer The system will cause the microcontroller to work abnormally or be damaged, and the detection function will be lost. Therefore, it is necessary to redesign the monitoring circuit that is suitable for using a single-chip microcomputer to realize a safe voltage undervoltage.

Contents of the invention

The purpose of the present invention is to address the deficiencies in the prior art, and propose a voltage undervoltage isolation monitoring circuit, which can protect the single-chip microcomputer from the influence of high voltage and strong electricity during voltage monitoring, and ensure the safe operation of the single-chip microcomputer monitoring system.

In order to achieve such purpose, the voltage undervoltage isolation monitoring circuit based on single-chip microcomputer of the present invention includes the isolation optocoupler adopted for realizing electrical isolation, the voltage reference chip that samples and compares the power supply voltage of the equipment, the monitored voltage of the primary side, and the power supply of the single-chip microcomputer. .

The concrete structure of the voltage undervoltage isolation monitoring circuit based on the single-chip microcomputer of the present invention is as follows:

The monitored power supply voltage first divides the voltage to the ground through a resistor, applies a voltage to the voltage sampling terminal of the power reference chip, and then applies a voltage to the anode of the primary side LED of the isolated optocoupler through the resistor, and the cathode of the isolated optocoupler LED is connected to the voltage reference chip The cathode of the voltage reference chip is grounded. The power supply voltage of the single-chip microcomputer is connected to the collector of the secondary side of the isolated optocoupler through a resistor, and the emitter of the secondary side of the isolated optocoupler is connected to the ground of the power supply of the single-chip microcomputer. On the collector of the secondary side of the isolated optocoupler, the voltage undervoltage protection signal will be output to the microcontroller.

When the monitored power supply voltage is a normal value, the voltage applied to the voltage sampling terminal of the voltage reference chip through the resistor divider is higher than the internal reference voltage of the chip, and the cathode to the anode of the voltage reference chip is conducting, isolating the primary side diode of the optocoupler If it is turned on, the secondary collector of the isolated optocoupler is at low level; once the monitored power supply voltage is lower than the normal value, the cathode to anode of the voltage reference chip will no longer conduct, and the primary diode of the isolated optocoupler will not conduct. When connected, the secondary collector of the isolated optocoupler jumps to a high level. The interrupt function of the single-chip microcomputer is triggered, and a signal of undervoltage is obtained.

The invention uses a voltage reference chip to sample and compare the power supply voltage of the equipment, and uses an isolated optocoupler to realize electrical isolation. This circuit structure makes the high voltage and strong electricity during voltage monitoring no longer affect the work of the single chip microcomputer due to the isolation of the optocoupler, and avoids electronic equipment. The occurrence of work failure or even damage ensures the safety and reliability of the single-chip microcomputer monitoring system.

Description of drawings

FIG. 1 is a schematic diagram of a voltage undervoltage isolation monitoring circuit based on a single-chip microcomputer in the present invention.

In Figure 1, O1 is the isolated optocoupler, R1 is the level pull-up resistor on the secondary side of the optocoupler, R2 is the current limiting resistor of the light-emitting diode on the primary side of the isolated optocoupler, R3 and R4 are voltage divider resistors, and TL431 is a voltage reference chip.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

The schematic diagram of the voltage undervoltage isolation monitoring circuit based on the single-chip microcomputer designed by the present invention is shown in Figure 1, including the isolation optocoupler O1 used to realize electrical isolation, and the voltage reference chip TL431 for sampling and comparing the power supply voltage of the equipment. Monitor power supply voltage VB, single-chip power supply VCC. The monitored power supply voltage VB is connected to the voltage dividing resistor R4 through the voltage dividing resistor R3, the other end of the voltage dividing resistor R4 is connected to the ground GND1 of the monitored power supply, and the voltage on the voltage dividing resistor R4 is added to the voltage sampling terminal R of the voltage reference chip , the monitored power supply voltage VB is also added to the anode of the primary side light-emitting diode of the isolated optocoupler O1 through the current limiting resistor R2, the cathode of the primary side light-emitting diode of the isolated optocoupler is connected to the cathode K of the voltage reference chip, and the anode of the voltage reference chip A is connected to the ground GND1 of the monitored power supply. The secondary collector of the isolated optocoupler is connected to the interrupt port INT of the single-chip microcomputer, and at the same time, it is connected to the single-chip power supply VCC through the level pull-up resistor R1, and the secondary emitter of the isolated optocoupler is connected to the ground of the single-chip power supply GND.

When the monitored power supply voltage VB is higher than the protection value, the voltage applied to the voltage sampling terminal R of the voltage reference chip TL431 through two voltage dividing resistors R3 and R4 is higher than the internal reference voltage of the chip, and the cathode K of the voltage reference chip TL431 It is connected to the anode A, and the primary side diode of the isolated optocoupler O1 is turned on, then the collector of the secondary side of the isolated optocoupler O1 is low level 0V; once the monitored power supply voltage VB is lower than the protection value, the voltage reference chip The cathode K of TL431 is no longer conducting to the anode A, and the primary side diode of the isolated optocoupler O1 is also not conducted, and the collector of the secondary side of the isolated optocoupler O1 jumps to the power supply voltage of the microcontroller, that is, high level. The interrupt function of the single-chip microcomputer is triggered, and the undervoltage signal of the monitored power supply voltage is obtained.

In one embodiment of the present invention, a circuit diagram as shown in FIG. 1 is adopted.

in:

The isolation optocoupler O1 is TLP521-1, R1=10k/0.25W, R2=3.3k/0.25W, R3=3.6K/0.25W, R4=1k/0.25W, R5=100k/0.25W, VB=12V, VCC = 5V.

Claims (1)

1, a kind of under-voltage isolating monitoring circuit, it is characterized in that comprising isolation optocoupler (O1), voltage reference chip (TL431), monitored supply voltage in former limit (VB) and microcontroller power supply (VCC), monitored supply voltage (VB) is through two divider resistance (R3, R4) connect the ground (GND1) of monitored power supply, voltage on second divider resistance (R4) is added in the voltage sample end (R) of voltage reference chip (TL431), monitored supply voltage (VB) is added to the anode of isolating the former limit of optocoupler (O1) light-emitting diode through current-limiting resistance (R2) simultaneously, the negative electrode of isolating the former limit of optocoupler light-emitting diode is received the negative electrode (K) of voltage reference chip, the anode of voltage reference chip (A) connects the ground (GND1) of monitored power supply, isolate the optical coupling secondary edges collector electrode and connect singlechip interruption mouth (INT), simultaneously connect microcontroller power supply (VCC), isolate the dynamo-electric seedbed (GND) of optical coupling secondary edges emitter order sheet through level pull-up resistor (R1).

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