Optocoupler isolated relay state detection circuit

Abstract

The utility model relates to a relay state detection circuit with optical coupling isolation, which comprises an optical coupling DT1, voltage dividing resistors RT80, RT81, RT82, RT83, RT85, and a diode DT81; the voltage dividing resistor RT85 and the reverse-connected diode DT81 are connected in parallel between two input ends of the optical coupling DT1; one input end of the optical coupling DT1 is connected to a power-on input UN of an electric meter through the voltage dividing resistors RT80, RT81, RT82 connected in series; the utility model has reasonable design, compact structure and convenient use.

Description

Technical Field

[0001] The utility model relates to a relay state detection circuit with optical coupling isolation. Background Art

[0002] As a general background introduction, a relay is a common switching element in automatic control systems. It can control large currents with small currents and play the role of automatic regulation, safety protection, and circuit conversion in circuits. An optocoupler is an isolation switch element. The primary signal is converted from electricity to light to electricity to control the conduction of the secondary circuit.

[0003] The meter relay is connected to the grid input terminal through a signal line, and is responsible for controlling the opening or closing of the grid input terminal at the application site of the energy meter. During the use of the energy meter, the applicant found that it might be necessary to control its opening and closing. After the meter is closed, the feedback detection circuit will immediately detect the level change, convert the signal into a record of the closing event, and send and store it to the meter processor. After the signal to control its shutdown is sent out, it is impossible to judge from the appearance whether it is really turned off. At this time, it is possible to detect whether the relay is really turned off by reading the relay closing record; moreover, during the use and maintenance of the meter, the closing and opening record is an important data of the meter's working condition. Therefore, it is very necessary to design an automatic detection circuit for the relay state. Utility Model Content

[0004] The technical problem to be solved by the utility model is generally to provide a relay state detection circuit with optical coupling isolation. At present, the external relay used in the electric energy meter controls the opening and closing of the grid input terminal. The utility model is an external relay feedback detection circuit, which detects the closing and closing state of the external relay in real time through optical coupling isolation.

[0005] In order to solve the above problems, the technical solution adopted by the utility model is:

[0006] In order to realize the detection of relays, a relay state detection circuit with optical coupling isolation includes an optical coupling DT1, voltage dividing resistors RT80, RT81, RT82, RT83, RT85, and a diode DT81;

[0007] Connect the voltage divider resistor RT85 and the reverse diode DT81 in parallel between the two input terminals of the optocoupler DT1;

[0008] One input end of the optocoupler DT1 is connected to the power-on input UN of the meter through the series-connected voltage-dividing resistors RT80, RT81, and RT82;

[0009] The other input terminal Connector L In of the optocoupler DT1 is connected to the external AC power;

[0010] An output terminal of the optocoupler DT1 is grounded;

[0011] The other output terminal Connector L Test of the optocoupler DT1 is connected to Connector L Test through a pull-up resistor RT84.

[0012] As a further improvement of the above technical solution:

[0013] In order to detect various states of AC power, a diode CT80 is connected between the two input terminals of the optocoupler DT1.

[0014] The detection circuit has an alternating current positive half-cycle state, an alternating current negative half-cycle state, and an alternating current transition state from a negative half-cycle to a positive half-cycle;

[0015] When in the positive half cycle of AC power, the optocoupler DT1 is in the on state, and the Connector L Test point is in the low level state connected to the ground;

[0016] When in the negative half cycle of AC power, the front-end voltage of optocoupler DT1 is in the clamping voltage state, optocoupler DT1 is in the cut-off state, and Connector L Test point is in the high level state pulled up to Connector L Test Power;

[0017] When the AC power changes from the negative half cycle to the positive half cycle, the voltage at the Connector L Test point is in a decreasing state, and the lowest value of the decreasing voltage is higher than the low level.

[0018] When the external relay is disconnected, that is, the Connector L In point is not connected to external AC power, the optocoupler DT1 is in a non-conducting state, and the Connector L Test is always in a high level state;

[0019] Connector L Test point is used to connect the meter MCU;

[0020] When the Connector L Test point is in a low level state, a power-off event is recorded.

[0021] The utility model detects the relay state in real time by means of feedback. When the external input is disconnected, the Connector L In immediately changes to a low level and transmits a signal to the processor to record the event, so that the time point of the switch-on or switch-off event can be accurately recorded.

[0022] The utility model uses an optical coupler as a switch to isolate strong electricity and weak electricity, has improved voltage resistance and strong anti-interference ability.

[0023] The utility model sets a suitable voltage-dividing resistor value at the front end of the optical coupler so that the optical coupler DT1 can be correctly turned on and off, thereby controlling the level of the Connector L Test point.

[0024] The utility model prevents the diode from being reversely broken down or the optical coupler DT1 from being broken down by selecting the diode DT81 with a large reverse withstand voltage value.

[0025] The utility model prevents the Connector L Test voltage from dropping too quickly to a low level when the voltage is converted from a negative half cycle to a positive half cycle by selecting a suitable capacitor CT80, thereby preventing a power-off event from being mistakenly recorded.

[0026] The utility model has the advantages of reasonable design, low cost, firmness and durability, safety and reliability, simple operation, time-saving, labor-saving, money-saving, compact structure and convenient use. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a circuit diagram of the utility model. DETAILED DESCRIPTION

[0028] like Figure 1 As shown, the optically-coupled isolated relay state detection circuit of this embodiment includes an optical coupler DT1, voltage-dividing resistors RT80, RT81, RT82, RT83, RT85, and a diode DT81;

[0029] Connect the voltage divider resistor RT85 and the reverse diode DT81 in parallel between the two input terminals of the optocoupler DT1;

[0030] One input end of the optocoupler DT1 is connected to the power-on input UN of the meter through the series-connected voltage-dividing resistors RT80, RT81, and RT82;

[0031] The other input terminal Connector L In of the optocoupler DT1 is connected to the external AC power;

[0032] An output terminal of the optocoupler DT1 is grounded;

[0033] The other output terminal Connector L Test of the optocoupler DT1 is connected to Connector L Test through a pull-up resistor RT84.

[0034] A diode CT80 is connected between the two input terminals of the optocoupler DT1.

[0035] Among them, UN is the power-on input of the meter, and Connector L In is connected to the external AC power. When the AC power is in the positive half cycle, DT1 is turned on, and the Connector L Test point is connected to the ground and becomes a low level. When the AC power is in the negative half cycle, under the action of diode DT81, the front-end voltage of the optocoupler is clamped at about -0.7V. At this time, the optocoupler is not turned on, and the Connector L Test point is pulled up to Connector L Test Power by RT84 and becomes a high level. When the AC power goes from the negative half cycle to the positive half cycle, due to the presence of capacitor CT80, the voltage at the Connector L Test point will only drop slowly and will not drop to a low level. Therefore, it can be considered that the voltage at this test point is a high level throughout the entire cycle.

[0036] When the external relay is disconnected, that is, the Connector L In point is not connected to external AC power, the optocoupler is not conducting, and Connector L Test is always at a high level.

[0037] When the meter MCU detects that the Connector L Test point changes to a low level, a power-off event is recorded.

[0038] The present invention is fully described for a clearer disclosure, and the prior art will not be listed one by one.

[0039] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the utility model, rather than to limit it; although the utility model is described in detail with reference to the above embodiments, ordinary technicians in the field should understand that they can still modify the technical solutions recorded in the above embodiments, or replace some of the technical features therein with equivalents; it is obvious for those skilled in the art to combine multiple technical solutions of the utility model. However, 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 utility model.

Claims

1. A relay state detection circuit with optical coupling isolation, characterized in that: Including optocoupler DT1, voltage divider resistors RT80, RT81, RT82, RT83, RT85, diode DT81; Connect the voltage divider resistor RT85 and the reverse diode DT81 in parallel between the two input terminals of the optocoupler DT1; One input end of the optocoupler DT1 is connected to the power-on input UN of the meter through the series-connected voltage-dividing resistors RT80, RT81, and RT82; The other input terminal Connector L In of the optocoupler DT1 is connected to the external AC power; An output terminal of the optocoupler DT1 is grounded; The other output terminal Connector L Test of the optocoupler DT1 is connected to Connector L Test through a pull-up resistor RT84.

2. The optically-coupled isolated relay state detection circuit according to claim 1, characterized in that: A diode CT80 is connected between the two input terminals of the optocoupler DT1.

3. The optically-coupled isolated relay state detection circuit according to claim 2, characterized in that: The detection circuit has an alternating current positive half-cycle state, an alternating current negative half-cycle state, and an alternating current transition state from a negative half-cycle to a positive half-cycle; When in the positive half cycle of AC power, the optocoupler DT1 is in the on state, and the Connector L Test point is in the low level state connected to the ground; When in the negative half cycle of AC power, the front-end voltage of optocoupler DT1 is in the clamping voltage state, optocoupler DT1 is in the cut-off state, and Connector L Test point is in the high level state pulled up to Connector L Test Power; When the AC power changes from the negative half cycle to the positive half cycle, the voltage at the Connector L Test point is in a decreasing state, and the lowest value of the decreasing voltage is higher than the low level.

4. The optically-coupled isolated relay state detection circuit according to claim 3, characterized in that: When the external relay is disconnected, that is, the Connector L In point is not connected to external AC power, the optocoupler DT1 is in a non-conducting state, and the Connector LTest is always in a high level state; Connector L Test point is used to connect the meter MCU; When the Connector L Test point is in a low level state, a power-off event is recorded.

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