Magnetic protection relay driving circuit for electric energy meter

Abstract

The utility model discloses a magnetic protection relay drive circuit for an electric energy meter, which comprises a power supply module, a control module and a drive switching module, and the drive switching module comprises a PMOS (P-channel Metal Oxide Semiconductor) tube V4, a triode V7, a relay K1, a relay K2, a resistor R7, a resistor R8, a resistor R11, a resistor R12 and a capacitor C13. According to the utility model, the triode is used for controlling the two relays to act synchronously, and the relays are used for controlling the current direction of the magnetic relay, so that higher driving current is provided, and meanwhile, the driving circuit also has the advantages of small number of devices, simple wiring, small occupied MCU pins and the like.

Description

Technical Field

[0001] The utility model relates to a relay driving circuit. Background Art

[0002] In a prepaid electric energy meter, a magnetic latching relay can control the on-off of a circuit according to the remaining power and working state of the electric energy meter.

[0003] The magnetic latching relay uses the magnetic force generated by a permanent magnet to maintain the on-off state of the contact, without continuous power supply, so as to achieve low-power operation. Its working principle is that when the contact of the relay needs to change the state, a positive (negative) DC pulse voltage is applied to excite the coil, and the relay completes the on-off state conversion instantaneously. After being in the holding state, the coil does not need to be continuously powered, and only relies on the magnetic force of the permanent magnet to maintain the state of the relay unchanged.

[0004] The existing driving method of the magnetic latching relay is as Figure 1 shown, using an NPN transistor and a PNP transistor for driving. However, with the implementation of the foreign electric energy meter technical standard IR46 and the release of new specifications in China's electric energy meter industry, the industry has put forward more stringent requirements for the magnetic latching relay of the electric energy meter, and the relay requires greater driving ability. In the traditional scheme, the current passes through multiple transistors during driving, and the driving ability is limited by the transistors, making it difficult to meet the new requirements, and there are also problems of a large number of devices and complex wiring. Summary of the Utility Model

[0005] The utility model provides a driving circuit for a magnetic latching relay of an electric energy meter, and its purpose is to solve the problems of insufficient driving ability, a large number of devices and complex wiring in the current driving circuit of the magnetic latching relay.

[0006] The technical solution of the utility model is as follows:

[0007] A driving circuit for a magnetic latching relay of an electric energy meter includes a power supply module, a control module and a driving switching module. The power supply module is used to supply power to the control module. The control module is used to send control signals to the driving switching module. The driving switching module is connected between the power supply module and the magnetic latching relay. The driving switching module includes a PMOS transistor V4, a transistor V7, a relay K1, a relay K2, a resistor R7, a resistor R8, a resistor R11, a resistor R12 and a capacitor C13;

[0008] The power supply module includes a driving power supply terminal VKT. The control module includes a control terminal RELAY-ON and a control terminal RELAY-OFF for sending control signals;

[0009] The driving power supply terminal VKT is connected to the source electrode of PMOS transistor V4, and is also connected to the gate electrode of PMOS transistor V4 through resistor R7. Capacitor C13 is connected in parallel with resistor R7. The gate electrode of PMOS transistor V4 is also connected to the control terminal RELAY-OFF through resistor R8.

[0010] The control terminal RELAY-ON is connected to the base electrode of transistor V7 through resistor R11, and is also connected to the emitter electrode of transistor V7 through resistor R12. The emitter electrode of transistor V7 is grounded.

[0011] One end of the coil of relay K1 is connected to the driving power supply terminal VKT, and the other end is connected to the collector electrode of transistor V7. The normally closed terminal of relay K1 is connected to the drain electrode of PMOS transistor V4, and the normally open terminal is grounded.

[0012] One end of the coil of relay K2 is connected to the driving power supply terminal VKT, and the other end is connected to the collector electrode of transistor V7. The normally closed terminal of relay K2 is grounded, and the normally open terminal is connected to the drain electrode of PMOS transistor V4.

[0013] The common terminal of relay K1 is used to be connected to the first driving connection terminal of the magnetic protection relay, and the common terminal of relay K2 is used to be connected to the second driving connection terminal of the magnetic protection relay.

[0014] As a further improvement of the driving circuit of the magnetic protection relay for the electric energy meter: The driving switching module further includes diode V5 and diode V6. Diode V5 is connected in parallel with the coil of relay K1, and its cathode is correspondingly connected to the driving power supply terminal VKT. Diode V6 is connected in parallel with the coil of relay K2, and its cathode is correspondingly connected to the driving power supply terminal VKT.

[0015] As a further improvement of the driving circuit of the magnetic protection relay for the electric energy meter: It further includes a power-on detection module for detecting the voltage of the driving power supply terminal VKT. The detection output terminal of the power-on detection module is connected to the control module.

[0016] As a further improvement of the driving circuit of the magnetic protection relay for the electric energy meter: The power-on detection module includes resistor R5, resistor R6 and capacitor C12. One end of resistor R5 is connected to the driving power supply terminal VKT, and the other end is connected to one end of resistor R6 and is connected to the detection output terminal POWER-UP. The other end of resistor R6 is grounded. Capacitor C12 is connected in parallel with resistor R6.

[0017] As a further improvement of the driving circuit of the magnetic protection relay for the electric energy meter: The ratio of the resistance value of resistor R5 to the resistance value of resistor R6 is 4 to 6.

[0018] As a further improvement of the magnetic protection magnetic relay driving circuit for the electric energy meter: The power supply module includes a transformer. The first tap of the transformer is connected to the input end of a rectifier V1. The positive pole of the output end of the rectifier V1 is the driving power supply terminal VKT, and the negative pole is grounded. A capacitor C1 is connected between the positive pole and the negative pole of the output end of the rectifier V1.

[0019] As a further improvement of the magnetic protection magnetic relay driving circuit for the electric energy meter: The control module includes an MCU.

[0020] Compared with the prior art, the present utility model has the following positive effects:

[0021] 1. In the present utility model, two relays are controlled to act synchronously through a triode, and then the current direction of the magnetic protection magnetic relay is controlled through the relays. The driving current of the magnetic protection magnetic relay only flows through the PMOS transistor and the contacts of relays K1 and K2, and does not pass through the triode. The magnitude of the current is only limited by the PMOS transistor, which can provide a driving current significantly higher than that of the traditional scheme. At the same time, it has the advantages of fewer components, simple wiring, and fewer MCU pin occupations.

[0022] 2. Diodes V5 and V6 are respectively connected in parallel at both ends of the coils of relays K1 and K2. When the current flowing through the coils disappears, the induced electromotive force generated by the coils does work and is consumed through the loop formed by the diodes and the coils, thereby preventing the triode V7 from being broken down and protecting the safety of the circuit.

[0023] 3. The control module can determine whether the electric energy meter starts successfully through the power-on detection module, providing a hardware basis for operations such as the control module sending an initial closing control signal after power-on. Description of the Drawings

[0024] Figure 1 is the circuit diagram of the driving circuit of the existing magnetic protection magnetic relay;

[0025] Figure 2 is the circuit diagram of the power supply module of the present utility model;

[0026] Figure 3 is the circuit diagram of the control module of the present utility model;

[0027] Figure 4 is the circuit diagram of the driving switching module of the present utility model;

[0028] Figure 5 is the circuit diagram of the power-on detection module of the present utility model. Detailed Description of the Embodiment

[0029] The technical solution of the present utility model will be described in detail below with reference to the drawings. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all of the embodiments.

[0030] A magnetic protection magnetic relay drive circuit for an electric energy meter, comprising a power supply module, a control module and a drive switching module.

[0031] The power supply module is used to supply power to the control module, the drive switching module, the magnetic protection magnetic relay, etc.

[0032] Specifically, as Figure 2 , the power supply module includes a transformer, a varistor, a thermistor, a transformer, a rectifier, a rectifier diode, an electrolytic capacitor and a three-terminal voltage regulator chip, etc.

[0033] The neutral wire of the 220V AC mains is connected to N, and the live wire is connected to L. The transformer converts the 220V AC into 3 isolated ACs:

[0034] 1. The first tap of the transformer is connected to the input end of the rectifier V1. The positive pole of the output end of the rectifier V1 is the drive power supply terminal VKT, which is used to supply power to the drive switching module and the magnetic protection magnetic relay. The negative pole of the output end is grounded. A capacitor C1 is connected between the positive and negative poles of the output end of the rectifier V1.

[0035] The output end of the rectifier V1 is also connected to the three-terminal voltage regulator chip D1 to output a stable voltage VCC to supply power to the control module.

[0036] 2. The second tap of the transformer passes through the rectifier diode V2, is connected to the electrolytic capacitor C3 and then connected to the three-terminal voltage regulator chip D2. The three-terminal voltage regulator chip D2 outputs the power supply VDD to supply power to the 485 communication chip.

[0037] 3. The third tap of the transformer passes through the rectifying diode V3, is connected to the electrolytic capacitor C5 for filtering and then connected to the three-terminal voltage regulator chip D3. The three-terminal voltage regulator chip D3 outputs the power supply LVDD to supply power to the electric energy meter metering chip to meet the electric energy meter metering function.

[0038] In this embodiment, D1, D2, and D3 are selected as Belling BL78L05D, and RV1 is selected as Xiwu'er's MYG3-20K420.

[0039] The control module is used to send control signals (tripping and closing commands) to the drive switching module.

[0040] Specifically, as Figure 3, the control module includes an MCU, and also includes a crystal oscillator G1, resistors (R1, R2, R3, R4), ceramic capacitors (C7, C8, C9, C10), etc. The crystal oscillator is used to provide timing for the MCU. The power supply VCC is connected to the VCC terminal and VBAT terminal of the MCU through a power supply filtering circuit composed of C9, C10, C11, R3, and R4 to supply power to the MCU. R1 and C7 are connected to the TEST of the MCU, and R2 and C8 are connected to the REST reset signal of the MCU to prevent the program from running wild.

[0041] The MCU is also provided with a control terminal RELAY-ON for sending control signals and a control terminal RELAY-OFF.

[0042] In this embodiment, the MCU is the Juquan platform HT6025 with a working voltage of 5V. G1 is a 32.768kHz crystal oscillator from Seiko Instruments Japan.

[0043] The drive switching module is connected between the power supply module and the magnetic protection magnetic relay.

[0044] Specifically, as Figure 4 , the drive switching module includes a PMOS transistor V4, a triode V7, relays K1, K2, a resistor R7, a resistor R8, a resistor R11, a resistor R12, and a capacitor C13.

[0045] The drive power supply terminal VKT is connected to the source electrode of the PMOS transistor V4, and is also connected to the gate electrode of the PMOS transistor V4 through a resistor R7. The capacitor C13 is connected in parallel with the resistor R7. The gate electrode of the PMOS transistor V4 is also connected to the control terminal RELAY-OFF through a resistor R8. The control terminal RELAY-OFF, R7, R8, C13, and V4 form a relay power supply control circuit to control whether to supply power to the magnetic protection magnetic relay. C13 is used to determine the charge and discharge time of the GS capacitor to solve the problem of voltage drop at VKT during the moment of MOS conduction. R8 is a gate drive resistor used to limit the current and prevent self-excitation oscillation of the MOS transistor. R7 is used to provide a bias voltage for the MOS transistor and serve as a discharge resistor for C13.

[0046] The control terminal RELAY-ON is connected to the base of the triode V7 through the resistor R11, and is also connected to the emitter of the triode V7 through the resistor R12. The emitter of the triode V7 is grounded. R11 is the base current-limiting resistor of V7 to prevent excessive base current flowing through the triode V7 from damaging the triode. The function of R12 is to prevent the triode from malfunctioning due to the influence of noise signals and make the transistor cut off more reliably. One end of the coil of the relay K1 is connected to the drive power supply terminal VKT, and the other end is connected to the collector of the triode V7. The normally closed terminal of the relay K1 is connected to the drain of the PMOS transistor V4, and the normally open terminal is grounded. One end of the coil of the relay K2 is connected to the drive power supply terminal VKT, and the other end is connected to the collector of the triode V7. The normally closed terminal of the relay K2 is grounded, and the normally open terminal is connected to the drain of the PMOS transistor V4. The common terminal of the relay K1 is used to connect to the first drive connection terminal of the magnetic protection magnetic relay, and the common terminal of the relay K2 is used to connect to the second drive connection terminal of the magnetic protection magnetic relay. The control terminal RELAY-ON, R11, R12, and V7 are used to control the synchronous operation of the relays K1 and K2, change the connection relationship between the magnetic protection magnetic relay and the drain of the PMOS transistor V4, so as to realize the action control of tripping and closing.

[0047] When the control terminal RELAY-OFF is at a high level, the PMOS transistor V4 is cut off. At this time, regardless of whether the control terminal RELAY-ON is at a high level or a low level, the magnetic protection magnetic relay is not powered on and is in a silent state (maintaining the original state unchanged).

[0048] When the control terminal RELAY-OFF is at a low level, the PMOS transistor V4 is turned on. At this time, the current direction of the magnetic protection magnetic relay is controlled by the control terminal RELAY-ON: If the control terminal RELAY-ON is at a high level, the triode V7 is turned on, and the relays K1 and K2 are switched simultaneously. The CM of each of K1 and K2 is changed to connect to the normally open terminal NO. The XS1-1 of the magnetic protection magnetic relay is grounded, and XS1-2 is connected to VKT to realize tripping; If the control terminal RELAY-ON is at a low level, the triode V7 is cut off, and the CM of the relays K1 and K2 are connected to the normally closed terminal NC. The XS1-1 of the magnetic protection magnetic relay is connected to VKT, and XS1-2 is grounded to realize closing. Note that during control, the control terminal RELAY-ON should be set first, and then the control terminal RELAY-OFF should be changed to a low level.

[0049] In this embodiment, K1 and K2 are Xiamen Hongfa miniature relays HF32F / 012-ZS3 with a rated drive voltage of 12V. The NPN transistor V7 is Leshan Radio L2SC1623RLT1G. R11 is valued according to the formula R = (VCC - 0.7) / Ib. The operating voltage of HT6025 is 5V, and the general value range is 2kΩ - 10kΩ, with the best recommended value being 2kΩ. The value range of R12 is 10kΩ - 100kΩ, and the recommended resistance value in this solution is 10kΩ. V4 is Leshan Radio PMOS LP2128LT1G with a drain-source breakdown voltage of 20V and a maximum continuous conduction current of 6A. The recommended value of C13 is 0.1uA. The recommended value of R8 is 10kΩ. The value range of R7 is 10k - 100kΩ, and the recommended value is 100kΩ.

[0050] Further, the drive switching module further includes diode V5 and diode V6. Diode V5 is connected in parallel with the coil of relay K1, and its cathode is correspondingly connected to the drive power supply terminal VKT. Diode V6 is connected in parallel with the coil of relay K2, and its cathode is correspondingly connected to the drive power supply terminal VKT. When the current flowing through the coil disappears, the induced electromotive force generated by the coil does work and is consumed through the loop formed by the diode and the coil, thereby preventing the transistor V7 from being broken down and protecting the safety of the circuit.

[0051] The magnetic protection magnetic relay drive circuit for the electric energy meter further includes a power-on detection module for detecting the voltage of the drive power supply terminal VKT, and the detection output terminal of the power-on detection module is connected to the control module.

[0052] As Figure 5 , in this embodiment, the power-on detection module includes resistor R5, resistor R6, and capacitor C12. One end of resistor R5 is connected to the drive power supply terminal VKT, the other end is connected to one end of resistor R6 and is connected to the detection output terminal POWER-UP, the other end of resistor R6 is grounded, and the capacitor C12 is connected in parallel with resistor R6.

[0053] The ratio of the resistance value of resistor R5 to the resistance value of resistor R6 is set according to the desired trigger voltage, generally 4 to 6. In this embodiment, R5 = 300kΩ and R6 = 56kΩ. That is, when VKT rises to 8V, the POWER-UP voltage reaches 1.24V. At this time, the MCU determines that the electric energy meter starts successfully. In the MCU, it can be set that after the POWER-UP voltage reaches 1.24V, wait for another 10s, and then actively send a closing command. This can ensure that the magnetic protection magnetic relay is in the closed state after power-on, avoiding the problem that the magnetic protection magnetic relay is accidentally disconnected due to jolting during transportation and cannot be powered on normally.

[0054] It should be noted that for those skilled in the art, it is obvious that the present utility model is not limited to the details of the above-mentioned exemplary embodiments, and without departing from the spirit or basic characteristics of the present utility model, the present utility model can be implemented in other specific forms. The scope of the present utility model is defined by the claims rather than the above description.

Claims

1. A magnetic protection relay driving circuit for an electric energy meter, comprising a power supply module, a control module and a drive switching module, wherein the power supply module is used to supply power to the control module, the control module is used to send a control signal to the drive switching module, and the drive switching module is connected between the power supply module and the magnetic protection relay, characterized in that: The drive switching module includes a PMOS tube V4, a transistor V7, a relay K1, a relay K2, a resistor R7, a resistor R8, a resistor R11, a resistor R12 and a capacitor C13; The power supply module includes a driving power supply terminal VKT, and the control module includes a control terminal RELAY-ON and a control terminal RELAY-OFF for sending a control signal; The driving power supply terminal VKT is connected to the source of the PMOS tube V4, and is also connected to the gate of the PMOS tube V4 through the resistor R7. The capacitor C13 is connected in parallel with the resistor R7. The gate of the PMOS tube V4 is also connected to the control terminal RELAY-OFF through the resistor R8. The control terminal RELAY-ON is connected to the base of the transistor V7 through the resistor R11, and is also connected to the emitter of the transistor V7 through the resistor R12, and the emitter of the transistor V7 is grounded; One end of the coil of relay K1 is connected to the driving power supply terminal VKT, and the other end is connected to the collector of transistor V7. The normally closed end of relay K1 is connected to the drain of PMOS tube V4, and the normally open end is grounded. One end of the coil of relay K2 is connected to the driving power supply terminal VKT, and the other end is connected to the collector of transistor V7. The normally closed end of relay K2 is grounded, and the normally open end is connected to the drain of PMOS tube V4. The common end of the relay K1 is used to be connected to the first driving connection end of the magnetic protection relay, and the common end of the relay K2 is used to be connected to the second driving connection end of the magnetic protection relay.

2. The magnetic protection relay driving circuit for an electric energy meter according to claim 1, characterized in that: The drive switching module further includes a diode V5 and a diode V6. The diode V5 is connected in parallel with the coil of the relay K1, and its cathode is correspondingly connected to the drive power supply terminal VKT. The diode V6 is connected in parallel with the coil of the relay K2, and its cathode is correspondingly connected to the drive power supply terminal VKT.

3. The magnetic protection relay driving circuit for an electric energy meter according to claim 1, characterized in that: It also includes a power-on detection module for detecting the voltage of the driving power supply terminal VKT, and the detection output terminal of the power-on detection module is connected to the control module.

4. The magnetic protection relay driving circuit for an electric energy meter as claimed in claim 3, characterized in that: The power-on detection module includes a resistor R5, a resistor R6 and a capacitor C12, one end of the resistor R5 is connected to the drive power supply terminal VKT, the other end is connected to one end of the resistor R6 and to the detection output terminal POWER-UP, the other end of the resistor R6 is grounded, and the capacitor C12 is connected in parallel with the resistor R6.

5. The magnetic protection relay driving circuit for an electric energy meter as claimed in claim 4, characterized in that: The ratio of the resistance value of the resistor R5 to the resistance value of the resistor R6 is 4 to 6.

6. The magnetic protection relay driving circuit for an electric energy meter according to any one of claims 1 to 5, characterized in that: The power supply module includes a transformer, a first tap of the transformer is connected to the input end of the rectifier V1, the positive pole of the output end of the rectifier V1 is the driving power supply end VKT, and the negative pole is grounded, and a capacitor C1 is connected between the positive and negative poles of the output end of the rectifier V1.

7. The magnetic protection relay driving circuit for an electric energy meter according to any one of claims 1 to 5, characterized in that: The control module includes an MCU.

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