An isolated control relay circuit for an electric energy meter

Abstract

The utility model discloses an isolation control relay circuit for electric energy meter, including MCU, photoelectric coupler isolator U1, photoelectric coupler isolator U2 and relay drive chip U3, the output end GPIO1 of MCU one way through resistance R1 with the anode electric connection of photoelectric coupler isolator U1 and another way with the cathode electric connection of photoelectric coupler isolator U2, the output end GPIO2 of MCU one way through resistance R2 with the anode electric connection of photoelectric coupler isolator U2 and another way with the cathode electric connection of photoelectric coupler isolator U1, the utility model discloses an isolation control relay circuit for electric energy meter, increases photoelectric coupler isolator between MCU and relay drive chip, and MCU control foot is designed into self -locking mode, even if control signal short time appears 11 level, and relay drive chip input foot also will not appear 11 simultaneously, thereby guaranteeing the reliable of drive chip.

Description

Technical Field

[0001] This utility model belongs to the field of relay control technology, specifically relating to an isolation control relay circuit for an electricity meter. Background Technology

[0002] Relays are one of the key components in the hardware design of electricity meters. Their reliability determines the lifespan of the electricity meter and is also related to operational safety. The design of relay control circuits needs to be reliable, stable, and have minimal external interference.

[0003] In a common solution, the MCU outputs two separate control signals, GPIO1 and GPIO2, which control the opening and closing of the relay via a driver chip. The MCU control signals are low-power signals, typically only a few tens of mA, while the relay is a high-power device (several amperes). Driving a high-power device with a low-power signal requires a driver chip. The logical relationship between the MCU control signals and the relay is as follows: Figure 3 As shown.

[0004] The relay's state is either open or closed, so control signals 1 0 and 0 1 are valid. When the control signal is 0 0, the driver chip enters sleep mode, and the 1 1 level logic is invalid. Therefore, the 1 1 situation should be avoided as much as possible during design.

[0005] Several common problems encountered in the practical use of relays:

[0006] 1) Significant Interference: Relay coils are inductive components. When current flows through them, they generate a magnetic field and store energy. At the moment of power failure, the current in the coil changes abruptly (decreases rapidly). According to Lenz's law, the coil generates an induced electromotive force (EMF) that opposes the change in current. This EMF is opposite in polarity to the original driving voltage, hence it is called a reverse EMF. For example, when a relay powered by DC 12V is de-energized, it may generate a reverse high voltage of tens of volts. This voltage has a significant impact on small signals in the MCU.

[0007] 2) Damaged driver chip: The MCU outputs logic 10 and 01, which switches the relay between open and closed states. Due to the slight delay or interference in the control signal output of 0 and 1, there is an extreme case where the output is 11. The output stage of the driver chip is a high-power push-pull output. In the case of 11, the upper and lower stage MOSFETs of the push-pull circuit may be turned on simultaneously, resulting in a short-term high current phenomenon, which may very likely burn out the driver chip.

[0008] Therefore, further improvements will be made to address the aforementioned issues. Utility Model Content

[0009] The main purpose of this utility model is to provide an isolation control relay circuit for an energy meter. An optocoupler isolator is added between the MCU and the relay driver chip. The MCU control pin is designed in a self-locking mode. Even if the control signal briefly shows an 11 level, the input pins (IN1, IN2) of the relay driver chip will not simultaneously show an 11 state, thereby ensuring the reliability of the driver chip.

[0010] To achieve the above objectives, this utility model provides an isolation control relay circuit for an energy meter, comprising an MCU, an optocoupler U1, an optocoupler U2, and a relay driver chip U3, wherein:

[0011] The output terminal GPIO1 of the MCU is electrically connected to the anode of the optocoupler U1 through resistor R1 and to the cathode of the optocoupler U2 through resistor R2; the output terminal GPIO2 of the MCU is electrically connected to the anode of the optocoupler U2 through resistor R2 and to the cathode of the optocoupler U1 through resistor R2.

[0012] The emitter of the optocoupler U1 is electrically connected to the input terminal IN1 (pin 1) of the relay driver chip U3 through resistor R4, and the emitter of the optocoupler U2 is electrically connected to the input terminal IN2 (pin 3) of the relay driver chip U3 through resistor R5.

[0013] The output terminals OUT1 (pin 7) and OUT2 (pin 6) of the relay driver chip U3 are electrically connected to the relay, respectively.

[0014] As a further preferred technical solution to the above technical solution, the input terminal IN1 of the relay driver chip U3 is grounded through resistor R7, and the input terminal IN2 of the relay driver chip U3 is grounded through resistor R8.

[0015] As a further preferred technical solution to the above technical solution, the ISET terminal of the relay driver chip U3 is grounded through resistor R6.

[0016] As a further preferred embodiment of the above technical solution, the collectors of both the optocoupler U1 and the optocoupler U2 are connected to the power supply terminal VDD via resistor R3.

[0017] As a further preferred technical solution to the above technical solution, the VCC terminal (pin 8, in addition to being connected to the power supply VCC) of the relay driver chip U3 is grounded through a capacitor. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the present invention.

[0019] Figure 2 This is the circuit schematic diagram of this utility model.

[0020] Figure 3 This is a diagram showing the logic relationship between MCU control signals and relays. Detailed Implementation

[0021] The following description is intended to disclose the present invention so that those skilled in the art can implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the present invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0022] This utility model discloses an isolation control relay circuit for an electricity meter. The specific embodiments of the utility model are further described below with reference to preferred embodiments.

[0023] In the embodiments of this utility model, those skilled in the art will note that the MCU and relays involved in this utility model can be considered as prior art.

[0024] Preferred embodiment.

[0025] like Figure 1-2 As shown, this utility model discloses an isolation control relay circuit for an energy meter, including an MCU, an optocoupler U1, an optocoupler U2, and a relay driver chip U3, wherein:

[0026] The output terminal GPIO1 of the MCU is electrically connected to the anode of the optocoupler U1 through resistor R1 and to the cathode of the optocoupler U2 through resistor R2; the output terminal GPIO2 of the MCU is electrically connected to the anode of the optocoupler U2 through resistor R2 and to the cathode of the optocoupler U1 through resistor R2.

[0027] The emitter of the optocoupler U1 is electrically connected to the input terminal IN1 (pin 1) of the relay driver chip U3 through resistor R4, and the emitter of the optocoupler U2 is electrically connected to the input terminal IN2 (pin 3) of the relay driver chip U3 through resistor R5.

[0028] The output terminals OUT1 (pin 7) and OUT2 (pin 6) of the relay driver chip U3 are electrically connected to the relay, respectively.

[0029] Specifically, the input terminal IN1 of the relay driver chip U3 is grounded through resistor R7, and the input terminal IN2 of the relay driver chip U3 is grounded through resistor R8.

[0030] More specifically, the ISET terminal of the relay driver chip U3 is grounded through resistor R6.

[0031] Furthermore, the collectors of both the optocoupler U1 and the optocoupler U2 are connected to the power supply terminal VDD via resistor R3.

[0032] Furthermore, the VCC terminal (pin 8, in addition to being connected to the power supply VCC) of the relay driver chip U3 is grounded through a capacitor.

[0033] Preferably, the optocoupler U1 / U2 is model QX816D, and the relay driver chip is model AL868.

[0034] The principle of this utility model is as follows:

[0035] When GPIO1=0 and GPIO2=1: the internal LED of the U2 optocoupler is turned on and emits light. After photoelectric conversion, the photosensitive device turns on the transistor, so IN2 is at a high level. At the same time, the U1 optocoupler is turned off and IN1 is at a low level. The relay driver chip (IN1, IN2) receives a level of 0 and 1, and the relay works in closed mode.

[0036] When GPIO1=1 and GPIO2=0: the internal LED of optocoupler U1 is turned on and emits light. After photoelectric conversion, the photosensitive device turns on the transistor, so IN1 is at a high level. At the same time, optocoupler U2 is turned off, and IN2 is at a low level. The relay driver chip (IN1, IN2) receives a level of 1 and 0, and the relay operates in the open mode.

[0037] When GPIO1=0 and GPIO2=0: the internal LEDs of optocouplers U1 and U2 are off, the phototransistor receiving the signal is also off, IN1 and IN2 are both low level (0 0), and the relay driver chip enters sleep mode.

[0038] When GPIO1=1 and GPIO2=1: the internal LEDs of U1 and U2 optocouplers are cut off, the receiving phototransistor is also cut off, IN1 and IN2 are both low level (0 0), and the relay driver chip enters sleep mode.

[0039] The self-locking crossover design avoids the situation where the input pins IN1 and IN2 of the driver chip are both high (1 1), thus preventing the driver chip from burning out.

[0040] And, as Figure 1-2As shown, the MCU control system is located to the left of the optocoupler, with GND as the reference ground (see the diagram above). The relay circuit is located to the right of the optocoupler, with PGND as the reference ground. By utilizing the optocoupler's opto-isolation technology, the signal is converted into an optical signal and then isolated by the optocoupler isolator, thus avoiding interference between the MCU and the relay.

[0041] It is worth mentioning that the MCU and relay technologies involved in this utility model patent application should be regarded as prior art. The specific structure, working principle, control method and spatial arrangement of these technologies can be adopted by conventional choices in the field and should not be regarded as the inventive point of this utility model patent. This utility model patent will not be further elaborated in detail.

[0042] For those skilled in the art, modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. An isolation control relay circuit for an electricity meter, characterized in that, It includes an MCU, optocoupler U1, optocoupler U2, and relay driver chip U3, wherein: The output terminal GPIO1 of the MCU is electrically connected to the anode of the optocoupler U1 through resistor R1 and to the cathode of the optocoupler U2 through resistor R2; the output terminal GPIO2 of the MCU is electrically connected to the anode of the optocoupler U2 through resistor R2 and to the cathode of the optocoupler U1 through resistor R2. The emitter of the optocoupler U1 is electrically connected to the input terminal IN1 of the relay driver chip U3 through resistor R4, and the emitter of the optocoupler U2 is electrically connected to the input terminal IN2 of the relay driver chip U3 through resistor R5. The output terminals OUT1 and OUT2 of the relay driver chip U3 are electrically connected to the relay, respectively.

2. The isolation control relay circuit for an energy meter according to claim 1, characterized in that, The input terminal IN1 of the relay driver chip U3 is grounded through resistor R7, and the input terminal IN2 of the relay driver chip U3 is grounded through resistor R8.

3. The isolation control relay circuit for an electricity meter according to claim 2, characterized in that, The ISET terminal of the relay driver chip U3 is grounded through resistor R6.

4. The isolation control relay circuit for an electricity meter according to claim 3, characterized in that, The collectors of both the optocoupler U1 and the optocoupler U2 are connected to the power supply terminal VDD via resistor R3.

5. The isolation control relay circuit for an energy meter according to claim 4, characterized in that, The VCC terminal of the relay driver chip U3 is grounded through a capacitor.

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