A power-on detection circuit and method for an electric energy meter

Abstract

An electric energy meter power-on detection circuit and method, the circuit comprising a power module, a threshold detection module, a start pulse module, a voltage detection module and a control module; the power supply signal end of the threshold detection module is connected with the first power supply of the power module, the output end of the threshold detection module is connected with the start pulse module and the voltage detection module respectively; the threshold detection module detects the voltage of the first power supply VIN, when the first power supply VIN is greater than the threshold Vz, the output voltage of the threshold detection module occurs step change; according to the voltage step change, the start pulse module outputs a single positive voltage pulse to the control module, and the voltage detection module outputs a logic level; the control module receives the single positive voltage pulse to trigger the interrupt hibernation wake-up, reads the logic level state output by the voltage detection module, and based on the logic level state, carries out the electric energy meter power-on detection, and guarantees the reliable operation of the electric energy meter in the complex working environment.

Description

Technical Field

[0001] This invention relates to the field of electricity meter technology, specifically to an electricity meter power-on detection circuit and method. Background Technology

[0002] As the legally mandated metering instrument for electricity billing, the long-term, highly reliable operation of electricity meters in various complex working environments has become one of the main demands of technical personnel in the industry. The increasingly complex power grid environment and current electricity load status necessitate higher requirements for the design of power-on detection systems for electricity meters.

[0003] Currently, there are generally two methods for power-on testing of electricity meters.

[0004] Method 1: The detection circuit detects the power-on status of the main power supply of the energy meter and confirms the power-on status signal by waking up the MCU from sleep mode. The drawback of this method is that the power-on start-up time of the energy meter is determined by the MCU sleep timer wake-up interval. Considering the battery life, the wake-up interval cannot be too small, and is usually on the order of seconds or more.

[0005] Method 2: Sample the main power supply voltage of the energy meter using a resistor divider method, and generate an interrupt signal using the voltage comparator function inside the MCU. This method requires the MCU to support the voltage comparator function in sleep mode, and because the voltage comparator function module is enabled in sleep mode, it increases the MCU's sleep power consumption and reduces battery life. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned problems existing in current power-on detection methods for electricity meters by proposing a power-on detection circuit and method for electricity meters to ensure reliable operation of electricity meters in complex working environments.

[0007] The technical solution of this invention is:

[0008] This invention provides a power-on detection circuit for an energy meter, comprising a power supply module, a threshold detection module, a start pulse module, a voltage detection module, and a control module; the power supply signal terminal of the threshold detection module is connected to the first power supply of the power supply module, and the output terminal of the threshold detection module is connected to the start pulse module and the voltage detection module respectively; the logic level output of the voltage detection module is connected to the corresponding input terminal of the control module.

[0009] The threshold detection module detects the voltage of the first power supply VIN. When the first power supply VIN is greater than the threshold Vz, the output voltage of the threshold detection module undergoes a step change.

[0010] Based on the voltage step change, the activation pulse module outputs a single positive voltage pulse to the control module, and the voltage detection module outputs a logic level.

[0011] The control module receives a single positive voltage pulse to trigger an interrupt wake-up from sleep mode, reads the logic level status output by the voltage detection module, and performs power-on detection of the energy meter based on the logic level status.

[0012] Furthermore, the threshold detection module includes a first Zener diode D1, a first resistor R1, and a second resistor R2. The cathode of the first Zener diode D1 is connected to a first power supply, and the anode of the first Zener diode D1 is connected to one end of the first resistor R1. The other end of the first resistor R1 is connected in series with the second resistor R2 and then grounded. The connection point of the first resistor R1 and the second resistor R2 serves as the output of the threshold detection module.

[0013] Furthermore, the start pulse module includes a first switch unit and a second switch unit. The input terminal of the first switch unit is connected to the output terminal of the threshold detection module, the output terminal of the first switch unit is connected to the input terminal of the second switch unit, and the output terminal of the second switch unit is connected to the corresponding input terminal of the control module.

[0014] Furthermore, the first switching unit includes a first capacitor C1, a third resistor R3, a fourth resistor R4, a fifth resistor R5, and an NPN transistor Q1. One end of the first capacitor C1 is connected to the output terminal of the threshold detection module, and the other end of the first capacitor C1 is connected to the third resistor R3 in series and then grounded. The connection point of the first capacitor C1 and the third resistor R3 is connected to the fourth resistor R4 in series and then connected to the base of Q1. The emitter of Q1 is grounded, and the collector is connected to the second power supply of the power supply module in series with the fifth resistor R5.

[0015] The second switching unit includes a sixth resistor R6, a PNP transistor Q2, and a seventh resistor R7. The connection point between the collector of Q1 and the fifth resistor R5 serves as the output of the first switching unit and is connected to the base of Q2. The emitter of Q2 is connected to the second power supply. The collector of Q2 is connected in series with the seventh resistor R7 and then grounded. The connection point between the collector of Q2 and the seventh resistor R7 is the output of the second switching unit, which serves as the output of the start pulse module and is connected to the corresponding input terminal of the control module.

[0016] Furthermore, the voltage detection module includes an eighth resistor R8, an NPN transistor Q3, and a ninth resistor R9. One end of the eighth resistor R8 is connected to the output of the threshold detection module, and the other end is connected to the base of Q3. The emitter of Q3 is grounded. The emitter of Q3 is connected in series with the ninth resistor R9 and then connected to the second power supply of the power supply module. The connection point between the ninth resistor R9 and the emitter of Q3 serves as the output of the voltage detection module.

[0017] Furthermore, the power module includes a first power supply and a second power supply. The first power supply is the DC power output from the AC / DC power module of the energy meter; the second power supply is the DC power supply provided by the first power supply after being stepped down and regulated, and the DC power supply provided by the battery power supply.

[0018] A method for detecting the power-on status of an electricity meter, based on the aforementioned circuit, the method comprising:

[0019] The threshold detection module detects the voltage of the first power supply VIN. When the first power supply VIN is greater than the threshold Vz, the output voltage of the threshold detection module undergoes a step change.

[0020] When the voltage step change occurs, the activation pulse module outputs a single positive voltage pulse to the control module, and the voltage detection module outputs a logic level.

[0021] The control module receives a single positive voltage pulse to trigger an interrupt wake-up from sleep mode, reads the logic level status output by the voltage detection module, and performs power-on detection of the energy meter based on the logic level status.

[0022] Furthermore, the threshold Vz is the regulated voltage of the first Zener diode D1.

[0023] Furthermore, the specific steps for the start-up pulse module to output a single positive voltage pulse are as follows:

[0024] The NPN transistor Q1 of the start pulse module changes its on / off state based on the step change of the rising edge of the output voltage of the threshold detection module, and the first switching unit of the start pulse module outputs a single negative voltage pulse signal.

[0025] The PNP transistor Q2 of the startup pulse module changes its on / off state based on the on / off state of the NPN transistor Q1, and the second switching unit of the startup pulse module outputs a single positive voltage pulse signal.

[0026] Furthermore, the control module reads the logic level state output by the voltage detection module, and performs power-on detection of the energy meter based on the logic level state as follows:

[0027] If the logic level is 0, it is determined that the mains power is on, and the control module is soft reset and the main program is run.

[0028] Otherwise, continue to hibernate and wait for the next hibernation interruption wake-up signal.

[0029] The beneficial effects of this invention are:

[0030] The power-on detection circuit and method for electricity meters of the present invention features a main power supply start-up threshold voltage design, a start-up pulse signal triggering wakeup from sleep interruption, and a determination of the power-on status of the electricity meter based on dual detection signals. It has the advantages of not increasing the power consumption of the battery in the sleep state and not being limited to the MCU main control chip. It achieves millisecond-level power-on start-up of the electricity meter, and has high reliability, simple circuit, and low cost.

[0031] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0032] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0033] Figure 1 A circuit diagram of the present invention is shown.

[0034] Figure 2 A flowchart illustrating the power-on detection process of an energy meter in an embodiment of the present invention is shown. Detailed Implementation

[0035] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0036] As attached Figure 1 As shown, this invention provides a power-on detection circuit for an electricity meter. The circuit includes: a power supply module 1, a threshold detection module 2, a start pulse module 3, a voltage detection module 4, and a control module 5. The threshold detection module 2 is connected to a first power supply 11, and the voltage change of the first power supply 11 controls the output of the threshold detection module 2. The start pulse module 3 and the voltage detection module 4 are connected to the threshold detection module 2 and to a second power supply 12. The threshold detection module 2 controls the output of the start pulse module 3 and the voltage detection module 4. The control module 5 is connected to the start pulse module 3, the voltage detection module 4, and the second power supply 12. The control module 5 is triggered by the positive voltage pulse signal output by the start pulse module 3 to wake up the MCU main control chip from sleep mode. The MCU main control chip of the control module 5 reads the logic level state output by the voltage detection module 4 and determines the power-on detection based on this logic level state.

[0037] As attached Figure 1As shown, the power module 1 in this embodiment includes a first power supply 11 (VIN) and a second power supply 12 (VDD). The first power supply 11 is the DC power output from the secondary side of the AC / DC switching power supply module of the energy meter; the second power supply 12 is provided by two power supplies, one being the DC power supply after step-down and stabilization of the first power supply 11, and the other being the output power supply from the battery power supply module; in this embodiment, the voltage of the first power supply 11 is 10V; the voltage of the second power supply 12 is 3.3V.

[0038] As attached Figure 1 As shown, the threshold detection module 2 in this embodiment includes a first power supply 11 (VIN), a Zener diode D1, a resistor R1, and a resistor R2. The cathode of the Zener diode D1 is connected to the first power supply 11, the resistor R1 is connected to the anode of the Zener diode D1, and the resistor R2 is connected between the resistor R1 and ground.

[0039] As attached Figure 1 As shown, the start pulse module 3 in this embodiment includes a first switch unit 31 and a second switch unit 32. The first switch unit 31 is connected to the threshold detection module 2, and the threshold detection module 2 controls the first switch unit 31 to be on or off. The second switch unit 32 is connected to the first switch unit 31, and the first switch unit 31 controls its on or off state.

[0040] Furthermore, the first switching unit 31 includes a second power supply 12 (VDD), a capacitor C1, resistors R3, R4, and R5, and an NPN transistor Q1. The capacitor C1 is connected to the threshold detection module 2, resistor R3 is connected between the capacitor C1 and ground, resistor R4 is connected between the capacitor C1 and the base of the NPN transistor Q1, the emitter of the NPN transistor Q1 is grounded, and resistor R5 is connected between the collector of the NPN transistor Q1 and the second power supply 12 (VDD).

[0041] Furthermore, the second switching unit 32 includes a second power supply 12 (VDD), a resistor R6, a PNP transistor Q2, and a resistor R7. Resistor R6 is connected between the first switching unit and the base of the PNP transistor Q2, the emitter of the PNP transistor Q2 is connected to the second power supply 12 (VDD), and resistor R7 is connected between the collector of the PNP transistor Q2 and ground.

[0042] As attached Figure 1 As shown, the voltage detection module 4 in this embodiment includes a second power supply 12 (VDD), a resistor R8, an NPN transistor Q3, and a resistor R9. The resistor R8 is connected between the threshold detection module 2 and the base of the NPN transistor Q3, the emitter of the NPN transistor Q3 is grounded, and the resistor R9 is connected between the second power supply 12 (VDD) and the emitter of the NPN transistor Q3.

[0043] As attached Figure 1As shown, the control module in this embodiment includes a second power supply 12 (VDD) and an MCU main control chip. The MCU main control chip is connected to the second power supply 12 (VDD), and the start pulse module 3 and voltage detection module 4 are connected to the MCU main control chip. The I / O port of the MCU main control chip connected to the start pulse module 3 supports sleep interrupt wake-up function.

[0044] Specifically, the power-on detection circuit in this embodiment operates as follows:

[0045] When the electricity meter is powered on, the first power supply 11 (VIN) rises rapidly from 0V to 10V. During the rise of VIN, when VIN is greater than the voltage regulation voltage Vz of the Zener diode D1, the Zener diode D1 is activated. The voltage across the Zener diode D1 is a fixed value Vz. Then the voltage across the resistor R2 is (VIN-Vz)×R2 / (R1+R2).

[0046] When the condition VIN is greater than Vz is met, the voltage across resistor R2 undergoes a step change. The threshold voltage Vz design can prevent the energy meter from being falsely triggered by abnormal voltage fluctuations in VIN under complex working environments, such as electricity theft by strong magnets.

[0047] Furthermore, when the voltage across resistor R2 jumps from 0V to (VIN-Vz)×R2 / (R1+R2), this voltage charges the RC circuit composed of capacitor C1, resistor R3, resistor R4, and the emitter of NPN transistor Q1.

[0048] When the charging time t = 0, the voltage across the equivalent resistance R of the RC circuit is (VIN - Vz). The NPN transistor Q1 is forward-biased at the emitter and reverse-biased at the collector, resulting in saturation conduction and a low-level output from the collector. As the charging time t gradually increases, the voltage across the equivalent resistance R gradually decreases. When this voltage no longer satisfies the forward bias of the NPN transistor Q1, Q1 is cut off, and a high-level output from the collector occurs. Consequently, a low-level pulse signal is output from the collector of the NPN transistor Q1.

[0049] It should be noted that during the process of NPN transistor Q1 from being turned on to being turned off, the base current of NPN transistor Q1 gradually decreases, and the voltage across the collector and emitter of NPN transistor Q1 gradually increases. This is reflected in the slow rise of the low-level pulse signal at the collector of NPN transistor Q1 from low level to high level.

[0050] It should be noted that by adjusting the RC time constant of the RC circuit, pulse signals with different pulse widths can be obtained. The pulse width can generally be adjusted in the range of tens of milliseconds to hundreds of milliseconds.

[0051] Furthermore, when the collector output of NPN transistor Q1 is low, PNP transistor Q2 is turned on, and the collector of PNP transistor Q2 is high; when the collector output of NPN transistor Q1 is high, PNP transistor Q2 is turned off, and the collector of PNP transistor Q2 is low; consequently, the collector of PNP transistor Q2 outputs a high-level pulse signal synchronized with the collector signal of NPN transistor Q1.

[0052] It should be noted that the PNP transistor Q2 switching unit optimizes the low-level pulse signal to high-level gradual rise problem of the NPN transistor Q1 switching unit.

[0053] Furthermore, when the voltage across resistor R2 changes from 0V to (VIN-Vz)×R2 / (R1+R2), NPN transistor Q3 turns on, and the collector of NPN transistor Q3 is at a low level; when the voltage across resistor R2 is 0V, NPN transistor Q3 turns off, and the collector of NPN transistor Q3 is at a high level.

[0054] Furthermore, the MCU main control unit circuit described in this embodiment includes a power supply VDD, an MCU main control chip, etc. The MCU main control chip is connected via an attached... Figure 2 The relevant control process enables the power meter to start up.

[0055] It should be noted that when the energy meter is not powered on, the Zener diode D1 is cut off, the NPN transistor Q1 is cut off, the PNP transistor Q2 is cut off, and the NPN transistor Q3 is cut off. The above power-on detection circuit does not consume the power of the second power supply 12, that is, it does not increase the power consumption of the battery power supply.

[0056] As attached Figure 2 As shown, the power-on detection process in this embodiment is as follows:

[0057] When the mains power to the electricity meter is cut off, the MCU enters sleep mode after the relevant power-down processing operations are performed.

[0058] After the mains power is restored to the electricity meter, the start pulse module 3 in this embodiment outputs a single positive voltage pulse signal (wakeup signal), which wakes up the MCU from sleep interruption. It then determines the wakeup source. If it is a wakeup from mains power, it reads the logic level status output by the voltage detection module 4 in this embodiment multiple times. If the level is 0, the MCU performs a soft reset and runs the main program. Otherwise, it checks the sleep state. If the condition is met, the MCU enters sleep mode again and waits for the next wakeup interrupt signal.

[0059] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A power-on detection circuit for an electricity meter, characterized in that: The circuit includes a power supply module (1), a threshold detection module (2), a start pulse module (3), a voltage detection module (4), and a control module (5); the power supply signal terminal of the threshold detection module (2) is connected to the first power supply (11) of the power supply module (1), and the output terminal of the threshold detection module (2) is connected to the start pulse module (3) and the voltage detection module (4) respectively; the logic level output of the voltage detection module (4) is connected to the corresponding input terminal of the control module (5); The threshold detection module (2) detects the voltage of the first power supply (11) VIN. When the first power supply (11) VIN is greater than the threshold Vz, the output voltage of the threshold detection module (2) undergoes a step change. Based on the voltage step change, the start pulse module (3) outputs a single positive voltage pulse to the control module (5), and the voltage detection module (4) outputs a logic level; The control module (5) receives a single positive voltage pulse to trigger an interrupt sleep wake-up, reads the logic level status output by the voltage detection module (4), and performs power-on detection of the energy meter based on the logic level status; If the logic level is 0, it is determined that the mains power is on, and the control module (5) performs a soft reset and runs the main program; Otherwise, continue to hibernate and wait for the next hibernation interruption wake-up signal; The start pulse module (3) includes a first switch unit (31) and a second switch unit (32). The input terminal of the first switch unit (31) is connected to the output terminal of the threshold detection module (2), the output terminal of the first switch unit (31) is connected to the input terminal of the second switch unit (32), and the output terminal of the second switch unit (32) is connected to the corresponding input terminal of the control module (5). The first switching unit (31) includes a first capacitor C1, a third resistor R3, a fourth resistor R4, a fifth resistor R5 and an NPN transistor Q1. One end of the first capacitor C1 is connected to the output terminal of the threshold detection module (2). The other end of the first capacitor C1 is connected to the third resistor R3 in series and then grounded. The connection point of the first capacitor C1 and the third resistor R3 is connected to the fourth resistor R4 in series and then connected to the base of Q1. The emitter of Q1 is grounded, and the collector is connected to the fifth resistor R5 in series and then connected to the second power supply (12) of the power supply module (1). The second switching unit (32) includes a sixth resistor R6, a PNP transistor Q2, and a seventh resistor R7. The connection point between the collector of Q1 and the fifth resistor R5 serves as the output of the first switching unit (31) and is connected to the base of Q2. The emitter of Q2 is connected to the second power supply (12). The collector of Q2 is connected in series with the seventh resistor R7 and then grounded. The connection point between the collector of Q2 and the seventh resistor R7 is the output of the second switching unit (32), which serves as the output of the start pulse module (3) and is connected to the corresponding input terminal of the control module (5).

2. The power-on detection circuit for an energy meter according to claim 1, characterized in that, The threshold detection module (2) includes a first Zener diode D1, a first resistor R1 and a second resistor R2. The cathode of the first Zener diode D1 is connected to the first power supply (11), and the anode of the first Zener diode D1 is connected to one end of the first resistor R1. The other end of the first resistor R1 is connected in series with the second resistor R2 and then grounded. The connection point of the first resistor R1 and the second resistor R2 serves as the output of the threshold detection module (2).

3. The power-on detection circuit for an energy meter according to claim 1, characterized in that, The voltage detection module (4) includes an eighth resistor R8, an NPN transistor Q3 and a ninth resistor R9. One end of the eighth resistor R8 is connected to the output of the threshold detection module (2), and the other end is connected to the base of Q3. The emitter of Q3 is grounded. The emitter of Q3 is connected in series with the ninth resistor R9 and then connected to the second power supply (12) of the power supply module (1). The connection point between the ninth resistor R9 and the emitter of Q3 serves as the output of the voltage detection module (4).

4. The power-on detection circuit for an energy meter according to claim 1, characterized in that, The power module (1) includes a first power supply (11) and a second power supply (12). The first power supply (11) is the DC power output from the AC / DC power module of the energy meter. The second power supply (12) is the DC power provided by the step-down and regulated DC power of the first power supply (11) and the battery power supply.

5. A method for detecting the power-on status of an electricity meter, based on the circuit described in any one of claims 1-4, characterized in that: The method includes: The threshold detection module (2) detects the voltage of the first power supply (11) VIN. When the first power supply (11) VIN is greater than the threshold Vz, the output voltage of the threshold detection module (2) undergoes a step change. When the voltage step change occurs, the start pulse module (3) outputs a single positive voltage pulse to the control module (5), and the voltage detection module (4) outputs a logic level; The control module (5) receives a single positive voltage pulse to trigger an interrupt sleep wake-up, reads the logic level status output by the voltage detection module (4), and performs power-on detection of the energy meter based on the logic level status.

6. The power-on detection method for an electricity meter according to claim 5, characterized in that, The threshold Vz is the regulated voltage of the first Zener diode D1.

7. The power-on detection method for an electricity meter according to claim 5, characterized in that, The starting pulse module (3) outputs a single positive voltage pulse as follows: The NPN transistor Q1 of the start pulse module (3) changes its on / off state based on the step change of the output voltage of the threshold detection module (2) and the first switching unit (31) of the start pulse module (3) outputs a single negative voltage pulse signal. The PNP transistor Q2 of the start pulse module (3) changes its on / off state based on the on / off state of the NPN transistor Q1, and the second switching unit (32) of the start pulse module (3) outputs a single positive voltage pulse signal.

8. The power-on detection method for an electricity meter according to claim 5, characterized in that, The specific steps for power-on detection of the energy meter based on logic level states are as follows: If the logic level is 0, it is determined that the mains power is on, and the control module (5) performs a soft reset and runs the main program; Otherwise, continue to hibernate and wait for the next hibernation interruption wake-up signal.

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