CN218449453U

CN218449453U - Relay switching-off circuit

Info

Publication number: CN218449453U
Application number: CN202222339134.9U
Authority: CN
Inventors: 葛雪军; 陈艳琴; 郑哲; 章跃平
Original assignee: Ningbo Sanxing Medical and Electric Co Ltd
Current assignee: Ningbo Sanxing Medical and Electric Co Ltd
Priority date: 2022-08-31
Filing date: 2022-08-31
Publication date: 2023-02-03
Anticipated expiration: 2032-08-31

Abstract

The utility model relates to a relay switching circuit, including MCU, its characterized in that: the switching-off control circuit comprises an MCU, a switching-off control end of a relay and a watchdog circuit, wherein the watchdog circuit comprises an input end connected with the MCU and an output end connected with the switching-off control end of the relay so as to periodically send a switching-off signal to the switching-off control end of the relay. The utility model has the advantages of: under the condition that the MCU is halted or works abnormally, a switching-out signal is periodically sent to a switching-out control end of the relay through the watchdog circuit, and the electric quantity loss caused by incapability of metering due to abnormal meter is avoided. In addition, the circuit is simple, the cost is low, and the normal use of the meter is not influenced.

Description

Relay switching-off circuit

Technical Field

The utility model relates to a switching off technical field, in particular to relay switching off circuit.

Background

The electric energy meter is an instrument for measuring electric energy, and along with popularization of electric equipment, the electric energy meter is more and more widely applied. At present, in the application of an electric energy meter, the power supply of electric equipment is controlled by controlling the on-off of a relay. For example, when the relay is switched off, the power supply equipment cannot supply power to the electric equipment; when the relay is switched on, the power supply equipment supplies power to the electric equipment, and the electric quantity of the electric equipment can be measured.

At present, an MCU sends an instruction to a relay, and a relay coil is triggered to be switched on or off through a relay driving circuit, so that a contact of the relay is switched on or off, and the purpose of switching on or switching off is achieved. However, once the MCU fails, normal metering cannot be performed, and the relay is always on and cannot be pulled off, so that a "power stealing event" occurs. Therefore, further improvement of the existing relay switching circuit is needed.

SUMMERY OF THE UTILITY MODEL

The utility model aims to solve the technical problem that a relay switching-off circuit that can regularly trigger the switching-off action when MCU trouble is provided to above-mentioned prior art.

The utility model provides a technical scheme that above-mentioned technical problem adopted does: the utility model provides a relay switching off circuit, includes MCU, its characterized in that: the switching-off control circuit comprises a MCU, a relay and a watchdog circuit, and is characterized by further comprising a watchdog circuit, wherein the watchdog circuit comprises an input end connected with the MCU and an output end connected with the switching-off control end of the relay, and the watchdog circuit periodically sends a switching-off signal to the switching-off control end of the relay.

In this scheme, the watchdog circuit includes:

the timing module comprises a reset pin, a first trigger signal output end and a second trigger signal output end, wherein the first trigger signal output end is connected with the switching-off control end of the relay;

one end of the driving module is correspondingly an input end of the watchdog circuit, and the other end of the driving module is correspondingly connected with a reset pin of the timing module;

one end of the pull-up circuit is connected between the reset pins of the driving module and the timing module;

the anode of the first diode is connected with the pull-up circuit, and the cathode of the first diode is connected with the first trigger signal output end; and

and the anode of the second diode is connected with the pull-up circuit, and the cathode of the second diode is connected with the second trigger signal output end.

Preferably, the timing module is a binary counter, a frequency divider or an oscillator chip.

The drive module comprises a third triode, a sixth triode, a seventh triode and a first capacitor, wherein an emitting electrode of the third triode, a collecting electrode of the seventh triode and a collecting electrode of the sixth triode are all connected with a power supply, the collecting electrode of the third triode is grounded and connected with a reset pin, a base electrode of the third triode is connected with the collecting electrode of the seventh triode, an emitting electrode of the seventh triode is grounded, a base electrode of the seventh triode is connected with the collecting electrode of the sixth triode through the first capacitor, the emitting electrode of the sixth triode is grounded, and the base electrode of the sixth triode corresponds to the input end of the watchdog circuit.

Preferably, the third transistor is a PNP transistor.

Preferably, the sixth triode is an NPN triode.

Preferably, the seventh transistor is an NPN transistor.

In this scheme, the pull-up circuit includes a first resistor and a second resistor connected in series, the other end of the first resistor is connected to the power supply, and the other end of the second resistor is connected to the reset pin.

In order to play the fool-proof role of the switching-off control end and the switching-on control end of the relay, the intelligent control device further comprises a second triode and a third resistor, wherein the base electrode of the second triode is connected with the switching-off control end of the relay through the third resistor, the emitting electrode of the second triode is grounded, and the collecting electrode of the second triode corresponds to the switching-on control end of the relay.

When the MCU works normally, the output end of the MCU outputs square waves with the frequency of f.

Compared with the prior art, the utility model has the advantages of: under the condition that the MCU is halted or works abnormally, a switching-out signal is periodically sent to a switching-out control end of the relay through the watchdog circuit, and the electric quantity loss caused by incapability of metering due to abnormal meter is avoided. In addition, the circuit is simple, the cost is low, and the normal use of the meter is not influenced.

Drawings

Fig. 1 is a circuit diagram of a relay switching circuit in an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following embodiments.

As shown in fig. 1, the relay switching circuit in this embodiment includes an MCU and a watchdog circuit. The watchdog circuit comprises an input end feed connected with the MCU and an output end connected with a switching-off control end RELAY _ B of the RELAY, and periodically sends a switching-off signal to the switching-off control end RELAY _ B of the RELAY.

The watchdog circuit in this embodiment includes a timing module N12, a driving module 1, a pull-up circuit 2, a first diode VD1, and a second diode VD2. The timing module N12 comprises a reset pin MR, a first trigger signal output end Qn and a second trigger signal output end Qm, wherein the first trigger signal output end Qn is connected with a switching-off control end RELAY _ B of the RELAY; one end of the driving module 1 is correspondingly an input end feed of the watchdog circuit, and the other end of the driving module 1 is correspondingly connected with a reset pin MR of the timing module N12; one end of the pull-up circuit 2 is connected between the reset pin MR of the driving module 1 and the timing module N12; the anode of the first diode VD1 is connected with the pull-up circuit 2, and the cathode of the first diode VD1 is connected with the first trigger signal output end Qn; the anode of the second diode VD2 is connected to the pull-up circuit 2, and the cathode of the second diode VD2 is connected to the second trigger signal output Qm.

The timing module N12 is a binary counter, a frequency divider or an oscillator chip; the MR of the timing module N12 is a reset pin, and the high level is effective; the resistor R103 and the capacitor C130 can be setThe minimum count period T of the timing module N12 is set, when the reset pin MR is at a high level, the timing module N12 is in a reset state, and the first trigger signal output terminal Qn is at a low level. When the reset pin MR is at a low level, the first trigger signal output terminal Qn outputs T = T × 2 ⁿ The high level/low level is inverted, n is the digit of the binary counter, and n is a positive integer.

As shown in fig. 1, the driving module 1 includes a third transistor V3, a sixth transistor V6, a seventh transistor V7 and a first capacitor C1, wherein an emitter of the third transistor V3, a collector of the seventh transistor V7 and a collector of the sixth transistor V6 are all connected to a power supply VDD, a collector of the third transistor V3 is grounded and connected to a reset pin MR, a base of the third transistor V3 is connected to a collector of the seventh transistor V7, an emitter of the seventh transistor V7 is grounded, a base of the seventh transistor V7 is connected to a collector of the sixth transistor V6 through the first capacitor C1, an emitter of the sixth transistor V6 is grounded, and a base of the sixth transistor V6 corresponds to an input feed of the watchdog circuit; certainly, the drive module 1 is also connected with a current-limiting resistor in series to prevent the triode from generating misoperation under the influence of a noise signal, so that the triode is cut off more reliably; in this embodiment, the third transistor V3 is a PNP transistor; the sixth triode V6 is an NPN triode; the seventh triode V7 is an NPN triode; in addition, the pull-up circuit 2 comprises a first resistor R1 and a second resistor R2 which are connected in series, the other end of the first resistor R1 is connected with a power supply VDD, and the other end of the second resistor R2 is connected with a reset pin MR.

In addition, the RELAY switching-off circuit further comprises a second triode V2 and a third resistor R3, wherein the base electrode of the second triode V2 is connected with the switching-off control end RELAY _ B of the RELAY through the third resistor R3, the emitter electrode of the second triode V2 is grounded, and the collector electrode of the second triode V2 corresponds to the switching-on control end RELAY _ a of the RELAY.

The working principle of the switching-off circuit of the relay in the embodiment is as follows:

when the MCU works normally, the output end of the MCU outputs square waves with the frequency f; the MCU generates a square wave with frequency f to act on an input end feed of the watchdog circuit, and under the action of a pull-up of a power supply VDD, a sixth triode V6, a seventh triode V7, a third triode V3, a first capacitor C1 and other resistors, a reset pin MR of the timing module N12 is ensured to trigger a high level once within t =1/f, so that the timing module N12 is reset;

the RELAY _ B controls the RELAY to be switched off, and the RELAY _ A controls the RELAY to be switched on. When RELAY _ B is high level and RELAY _ A is low level, the RELAY will be switched off; the second triode V2 ensures that the RELAY _ A is at a low level when the RELAY _ B is at a high level;

when the input end feed of the watchdog circuit is continuously high level/low level/no level (MCU abnormal/dead halt), no current flows through the first capacitor C1, the seventh triode V7 and the third triode V3 will not be conducted, and the reset pin MR level of the timing module N12 at this time is controlled by the states of the first resistor R1, the second resistor R2, the resistor R104, the first trigger signal output terminal Qn and the second trigger signal output terminal Qm; when the first trigger signal output end Qn and the second trigger signal output end Qm are not triggered, both the first trigger signal output end Qn and the second trigger signal output end Qm are at a low level; so when the reset pin MR of the timing module N12 is low, the second trigger signal output Qm performs T = T × 2 ^m High and low level inversion is carried out, and the first trigger signal output end Qn carries out T = T × 2 ⁿ Turning over, wherein m is less than n; t2 of the second trigger signal output terminal Qm ^m When the high-low level reversal occurs after the time expiration, T = T × 2 of the first trigger signal output end at the time ⁿ The time is not yet reached, so that the high-low level inversion does not occur, and therefore, the switching-off operation cannot be executed at this time, until when the first trigger signal output end Qn is at a high level, and the second trigger signal output end Qm is also at a high level, the RELAY _ B is at a high level, and the RELAY is switched off when the RELAY is at a low level. In this combination, a delay of T = T × 2 is formed ⁿ Action T = T × 2 ^m The switching-off operation of the switch.

The overall function is that when the MCU crashes or is abnormal, T = T × 2 is passed ⁿ T = T × 2 is triggered ^m The switching-off action of the hardware watchdog is realized to control the switching-off of the relay.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of improvements and decorations can be made without departing from the technical principle of the present invention, and these improvements and decorations should also be regarded as the protection scope of the present invention.

Claims

1. The utility model provides a relay switching off circuit, includes MCU, its characterized in that: the circuit comprises an MCU (microprogrammed control unit), a RELAY, a watchdog circuit and a RELAY, wherein the watchdog circuit comprises an input end (feed) connected with the MCU and an output end connected with a switching-off control end (RELAY _ B) of the RELAY, and the watchdog circuit periodically sends a switching-off signal to the switching-off control end (RELAY _ B) of the RELAY.

2. The relay trip circuit of claim 1, wherein: the watchdog circuit includes:

the timing module (N12) comprises a reset pin (MR), a first trigger signal output end (Qn) and a second trigger signal output end (Qm), wherein the first trigger signal output end (Qn) is connected with a switching-off control end (RELAY _ B) of the RELAY;

one end of the driving module (1) is correspondingly an input end (feed) of the watchdog circuit, and the other end of the driving module (1) is correspondingly connected with a reset pin (MR) of the timing module (N12);

one end of the pull-up circuit (2) is connected between the drive module (1) and a reset pin (MR) of the timing module (N12);

the positive electrode of the first diode (VD 1) is connected with the pull-up circuit (2), and the negative electrode of the first diode (VD 1) is connected with the first trigger signal output end (Qn); and

and the anode of the second diode (VD 2) is connected with the pull-up circuit (2), and the cathode of the second diode (VD 2) is connected with the second trigger signal output end (Qm).

3. The relay trip circuit of claim 2, wherein: the timing module (N12) is a binary counter, a frequency divider or an oscillator chip.

4. The relay trip circuit of claim 2, wherein: the drive module (1) comprises a third triode (V3), a sixth triode (V6), a seventh triode (V7) and a first capacitor (C1), wherein the emitter of the third triode (V3), the collector of the seventh triode (V7) and the collector of the sixth triode (V6) are all connected with a power supply (VDD), the collector of the third triode (V3) is grounded and connected with a reset pin (MR), the base of the third triode (V3) is connected with the collector of the seventh triode (V7), the emitter of the seventh triode (V7) is grounded, the base of the seventh triode (V7) is connected with the collector of the sixth triode (V6) through a first capacitor (C1), the emitter of the sixth triode (V6) is grounded, and the base of the sixth triode (V6) corresponds to the input end (feed) of the watchdog circuit.

5. The relay trip circuit of claim 4, wherein: the third triode (V3) is a PNP triode.

6. The relay trip circuit of claim 4, wherein: the sixth triode (V6) is an NPN triode.

7. The relay trip circuit of claim 4, wherein: the seventh triode (V7) is an NPN triode.

8. The relay trip circuit of claim 2, wherein: the pull-up circuit (2) comprises a first resistor (R1) and a second resistor (R2) which are connected in series, the other end of the first resistor (R1) is connected with a power supply (VDD), and the other end of the second resistor (R2) is connected with a reset pin (MR).

9. The relay trip circuit according to any one of claims 1 to 8, characterized in that: the switching-on control circuit further comprises a second triode (V2) and a third resistor (R3), the base electrode of the second triode (V2) is connected with the switching-off control end (RELAY _ B) of the RELAY through the third resistor (R3), the emitting electrode of the second triode (V2) is grounded, and the collecting electrode of the second triode (V2) corresponds to the switching-on control end (RELAY _ A) of the RELAY.

10. The relay trip circuit of claim 9, wherein: and when the MCU works normally, the output end of the MCU outputs square waves with the frequency of f.