CN115932386A - Electric energy metering circuit and electric energy metering device - Google Patents
Electric energy metering circuit and electric energy metering device Download PDFInfo
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Abstract
The application provides an electric energy metering circuit and electric energy metering device, wherein, the electric energy metering circuit includes switching power supply circuit, power failure detection circuit and treater, switching power supply circuit is including the first rectifier circuit that connects gradually, voltage isolating circuit, high-pressure energy storage electric capacity, step-down converting circuit, second rectifier circuit and low pressure energy storage electric capacity, input voltage through to voltage isolating circuit detects, when being less than power failure threshold voltage and switching power supply normal operating, detect in advance and fall the electricity, and through high-pressure energy storage electric capacity, can prolong by a wide margin and fall the electric data storage time, ensure data storage safety, simultaneously under the prerequisite of guaranteeing data storage safety, can reduce the appearance value of low pressure energy storage electric capacity, reduce design cost, and the method that adopts the outside interrupt in cooperation, can further fall the real-time nature that detects in advance, guarantee data storage's safety more.
Description
Technical Field
The application belongs to the technical field of metering, and particularly relates to an electric energy metering circuit and an electric energy metering device.
Background
With the technical development and the improvement of living standards of people, electric energy becomes a more indispensable energy source in production and living of people, wherein electric energy metering products such as an electric energy meter and a concentrator influence the settlement of electric energy trade expenses and are metering devices for legal key management of various countries at home and abroad, so the electric energy metering products need to store electric energy metering, event recording and other important data into a nonvolatile memory within a limited time when external alternating current is required to be powered off, the accuracy of the important data is ensured, the popularization of smart electric meters in markets at home and abroad at present, more power-off storage data are used originally, and the timeliness of power-off detection is very important.
In the power meter reading products such as electric energy meters and concentrators in the power meter industry, power supplies mainly comprise a switching power supply and a linear power supply, and most of the power supplies are supplied by a flyback switching power supply.
The power failure detection of the existing electric energy meter and concentrator mainly has two modes:
firstly, the voltage of the output end of the AC-DC step-down transformer is detected, please refer to the attached drawing 1, wherein the power failure detection time is delayed, the power failure data storage is supported only by the discharge of an energy storage capacitor at the output end of the step-down transformer, the power failure time is short, and the data storage risk is large.
And secondly, alternating current input voltage detection is realized, please see attached figure 2, a sampling resistor and MCU are adopted to carry the A/D or directly read a voltage sampling value of a metering chip, the sampling rate of the sampling resistor and the MCU is limited by the A/D and the sampling conversion rate of the metering chip, the power failure detection time is less in advance than that of the first mode, power failure data storage is supported by discharging of an energy storage capacitor at the output end of a step-down transformer, and the risk of data storage is high.
In addition, in the two modes, the MCU is adopted to carry out A/D sampling of resources and an external detection circuit or the MCU is adopted to carry out judgment of power failure detection, a scanning method is adopted, please refer to the attached drawing 3, timing scanning is carried out in a main cycle or a timing interruption, timeliness of power failure detection is not high, and data storage risk is large.
Disclosure of Invention
The application aims to provide an electric energy metering circuit, and aims to solve the problems that the power failure detection is not timely and the data storage risk is large in the conventional power failure detection circuit and detection method.
The first aspect of the embodiment of the application provides an electric energy metering circuit, which comprises a switching power supply circuit, a power failure detection circuit and a processor;
the switch power supply circuit comprises a first rectifying circuit, a voltage isolating circuit, a high-voltage energy storage capacitor, a voltage reduction conversion circuit, a second rectifying circuit and a low-voltage energy storage capacitor which are connected in sequence, wherein the second rectifying circuit and the low-voltage energy storage capacitor are also connected with a power supply end of a system circuit;
the power failure detection circuit is connected with the input end of the voltage isolation circuit and used for detecting the input voltage of the voltage isolation circuit and outputting an external interrupt level signal when the input voltage is smaller than the power failure threshold voltage;
and the processor is respectively connected with the system circuit and the processor and is used for acquiring a working power supply through the system circuit and carrying out power failure judgment and data storage work after power failure according to the external interrupt level signal.
Optionally, the step-down conversion circuit includes a step-down transformer and a switching power supply chip;
the primary winding of the step-down transformer is respectively connected with the signal end of the switching power supply chip, the output end of the voltage isolation circuit and the power supply end of the high-voltage energy storage capacitor, and the secondary winding of the step-down transformer is connected with the input end of the second rectification circuit.
Optionally, the voltage isolation circuit comprises a diode;
and the anode and the cathode of the diode respectively form the input end and the output end of the voltage isolation circuit.
Optionally, the power down detection circuit includes:
the voltage sampling circuit is connected with the input end of the voltage isolation circuit and is used for sampling the input voltage of the voltage isolation circuit in a voltage division mode and outputting the sampling voltage;
the protection circuit is connected with the output end of the voltage sampling circuit and is used for voltage protection and filtering;
the voltage detection circuit is connected with the output end of the protection circuit and used for comparing the sampling voltage output by the protection circuit with the power-down threshold voltage and outputting an external interrupt level signal;
the signal isolation circuit is connected with the output end of the voltage detection circuit and is used for carrying out signal isolation output on the external interrupt level signal;
and the signal conversion circuit is connected with the output end of the signal isolation circuit and is used for shaping and outputting the external interrupt level signal.
Optionally, the voltage sampling circuit comprises a first resistor and a second resistor;
the first end of first resistance constitutes the input of voltage sampling circuit, the second end of first resistance with the first end of second resistance is connected and is constituted the output of voltage sampling circuit, the second end and the first earthing terminal of second resistance are connected.
Optionally, the protection circuit comprises a transient diode, a third resistor and a first capacitor;
the cathode of the transient diode, the first end of the third resistor and the output end of the voltage sampling circuit are connected, the second end of the transient diode is connected with the first grounding end, the second end of the third resistor and the first end of the first capacitor are connected together to form the output end of the protection circuit, and the second end of the first capacitor is connected with the first grounding end.
Optionally, the voltage detection circuit comprises a first electronic switch tube;
the first end of the first electronic switch tube forms the output end of the voltage detection circuit, the second end of the first electronic switch tube is connected with the first grounding end, and the controlled end of the first electronic switch tube forms the input end of the voltage detection circuit.
Optionally, the signal isolation circuit includes a fourth resistor, a fifth resistor, an optocoupler, and a second capacitor;
the first end of the fourth resistor and the first end of the second capacitor are connected with a positive power supply end, the second end of the fourth resistor is connected with the anode of the diode of the optocoupler, the cathode of the diode of the optocoupler forms the input end of the signal isolation circuit, the collector of the triode of the optocoupler and the first end of the fifth resistor are connected together to form the output end of the signal isolation circuit, the emitter of the triode of the optocoupler is connected with a second grounding end, and the second end of the fifth resistor is connected with the positive power supply end.
Optionally, the signal conversion circuit includes a sixth resistor, a seventh resistor, a third capacitor, and a second electronic switching tube;
the first end of the sixth resistor forms an input end of the signal conversion circuit, the second end of the sixth resistor is connected with a controlled end of the second electronic switching tube, the first end of the seventh resistor and the first end of the third capacitor are connected together to form an output end of the signal conversion circuit, the second end of the second electronic switching tube, the second end of the seventh resistor and the second end of the third capacitor are connected with a second grounding end, and the second end of the sixth resistor is connected with a positive power supply end.
A second aspect of the embodiments of the present application provides an electric energy metering device, including the electric energy metering circuit as described above.
Compared with the prior art, the embodiment of the application has the advantages that: the electric energy metering circuit detects the input voltage of the voltage isolation circuit, detects power failure in advance when the input voltage is lower than the power failure threshold voltage and the switching power supply works normally, can greatly prolong the power failure data storage time through the high-voltage energy storage capacitor, ensures the safety of data storage, can reduce the capacitance value of the low-voltage energy storage capacitor on the premise of ensuring the safety of data storage, reduces the design cost, adopts an external interruption method in a matching manner, can further detect the power failure in advance, and ensures the safety of data storage more.
Drawings
Fig. 1 is a schematic diagram of a first structure of a conventional power down detection circuit;
fig. 2 is a schematic diagram of a second structure of a conventional power down detection circuit;
FIG. 3 is a schematic flow chart of a conventional power down detection method;
fig. 4 is a schematic structural diagram of an electric energy metering circuit provided in an embodiment of the present application;
FIG. 5 is a schematic circuit diagram of an electric energy metering circuit provided in an embodiment of the present application;
FIG. 6 is a schematic structural diagram of a power-down detection circuit in the electric energy metering circuit shown in FIG. 1;
FIG. 7 is a schematic circuit diagram of a power down detection circuit in the power metering circuit shown in FIG. 1;
fig. 8 is a schematic flow chart of a power failure detection method provided in an embodiment of the present application.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.
A first aspect of the embodiments of the present application provides an electric energy metering circuit, as shown in fig. 4, the electric energy metering circuit includes a switching power supply circuit 100, a power failure detection circuit 300, and a processor 400.
The switching power supply circuit 100 comprises a first rectifying circuit 10, a voltage isolation circuit 20, a high-voltage energy-storage capacitor 30, a voltage-reduction conversion circuit 40, a second rectifying circuit 50 and a low-voltage energy-storage capacitor 60 which are connected in sequence, wherein the second rectifying circuit 50 and the low-voltage energy-storage capacitor 60 are also connected with a power supply end of a system circuit 200;
a power-down detection circuit 300 connected to an input terminal of the voltage isolation circuit 20, for detecting an input voltage of the voltage isolation circuit 20 and outputting an external interrupt level signal when the input voltage is less than a power-down threshold voltage;
and the processor 400 is connected with the system circuit 200 and the processor 400 respectively, and is configured to obtain a working power through the system circuit 200, and perform power failure determination and data storage after power failure according to an external interrupt level signal.
In this embodiment, the first rectifying circuit 10 is configured to perform rectification conversion on an input first ac power and output a first dc power, the voltage isolating circuit 20 is configured to perform voltage isolation output on the first dc power, and the high-voltage energy-storage capacitor 30 is connected to an output end of the voltage isolating circuit 20 and configured to perform high-voltage energy storage.
The step-down converting circuit 40 is connected to the output terminal of the voltage isolating circuit 20 and the power terminal of the high-voltage energy-storage capacitor 30, and is configured to perform ac/dc and step-down conversion on the first dc power, and output the second ac power after step-down to the second rectifying circuit 50, the second rectifying circuit 50 is connected to the output terminal of the step-down converting circuit 40 and the power terminal of the system circuit 200, and is configured to perform rectification conversion on the second ac power, and output the second dc power to the system circuit 200, the low-voltage energy-storage capacitor 60 is connected to the output terminal of the second rectifying circuit 50 and the power terminal of the system circuit 200, and is configured to receive the second dc power and perform low-voltage energy storage, and supply power to the system circuit 200 when power failure occurs.
The first rectification circuit 10 and the second rectification circuit 50 may adopt corresponding rectification bridges, diodes and other structures, meanwhile, the second rectification circuit 50 may be provided with one or more paths according to the power supply requirement of the system circuit, optionally, as shown in fig. 5, the first rectification circuit 10 adopts a rectification bridge composed of four diodes, such as diodes D1 to D4, and the second rectification circuit 50 is composed of diodes, such as diodes D20, D21 and the like.
The voltage isolation circuit 20 is used for preventing voltage backflow, the output voltage of the first rectification circuit 10 drops along with the reduction of the external alternating current input voltage, the high-voltage energy storage capacitor 30 has an energy storage effect, and the voltage backflow prevention effect of the voltage isolation circuit 20 is matched, so that the voltage dropping speed of the high-voltage energy storage capacitor 30 is lower than that of the first rectification circuit 10 at the front end.
The voltage isolation circuit 20 may adopt a relay, a diode, etc., and optionally, as shown in fig. 5, the voltage isolation circuit 20 adopts a diode D17, and an anode and a cathode of the diode respectively form an input terminal and an output terminal of the voltage isolation circuit 20. The specific type can be selected according to the voltage isolation requirement, for example, the type is M20, the maximum reverse withstand voltage is 2000V, and the diode with the forward rectification current 1A is selected, and the specific type is not limited.
Alternatively, the high voltage energy storage capacitor 30 may be an electrolytic capacitor, such as the first electrolytic capacitor C2 and the second electrolytic capacitor C3 shown in fig. 5.
The low voltage energy storage capacitor 60 may be a storage capacitor of a conventional structure, such as capacitors C9, C10, C12, C13, etc. shown in fig. 5.
Optionally, as shown in fig. 5, the step-down conversion circuit 40 includes a step-down transformer T1 and a switching power supply chip U1, a primary winding of the step-down transformer T1 is connected to a signal end of the switching power supply chip U1, an output end of the voltage isolation circuit 20 and a power end of the high-voltage energy-storage capacitor 30, and a secondary winding of the step-down transformer T1 is connected to an input end of the second rectification circuit 50.
Wherein, switching power supply chip U1 controls step-down transformer T1 to carry out the interchange step-down conversion to output second alternating current power supply to second rectifier circuit 50, during normal work, switching power supply chip U1 is supplied power by the first direct current power supply of voltage isolation circuit 20 output, and after falling the electric, provide working power supply by high-voltage energy storage capacitor 30, switching power supply chip U1 is greater than self working power supply's time at input voltage within, continue to control step-down transformer T1 and carry out the interchange step-down conversion work.
The system circuit 200 includes a power conversion circuit, a communication circuit, and the like, where the power conversion circuit is configured to convert a received power signal into a corresponding working power and provide the working power to the processor 400, the communication circuit, and the like.
The processor 400 may be a single chip, an MCU, or the like, and the specific structure is not limited.
When the electric energy metering circuit normally inputs a first alternating current power supply, for example, when the commercial power is supplied, the first rectifying circuit 10, the voltage isolating circuit 20, the step-down converting circuit 40 and the second rectifying circuit 50 sequentially perform primary rectifying, voltage isolating, step-down converting and secondary rectifying operations, and meanwhile, the high-voltage energy storage capacitor 30 and the low-voltage energy storage capacitor 60 perform charging energy storage and are reserved for standby output.
When power failure occurs, the high-voltage energy storage capacitor 30 starts to supply power to the rear-end module, and the power supply comprises a step-down transformer T1 and a switching power supply chip U1 which output a direct-current power supply to the step-down conversion circuit 40, the step-down transformer T1 and the second rectifying circuit 50 normally perform alternating-current step-down conversion and rectification work, the system circuit 200 is continuously supplied with power by the second rectifying circuit 50, when the high-voltage energy storage capacitor 30 discharges, the terminal voltage of the high-voltage energy storage capacitor decreases, the input voltage of the step-down transformer T1 and the working voltage of the switching power supply chip U1 decrease, until the input voltage provided by the step-down transformer T1 and/or the working voltage of the switching power supply chip U1 provided by the high-voltage energy storage capacitor 30 decrease to a voltage threshold, the step-down conversion circuit 40 stops working, meanwhile, the system circuit 200 is supplied with power by the low-voltage energy storage capacitor 60, and the system circuit 200 and the processor 400 stop working until the terminal voltage output by the low-voltage energy storage capacitor 60 is smaller than the working voltage of the system circuit 200 and/or the processor 400.
Meanwhile, during power failure detection, the power failure detection circuit 300 directly detects the input voltage of the voltage isolation circuit 20, detects a power failure event and outputs an external interrupt level signal when detecting that the input voltage of the voltage isolation circuit 20 is smaller than the power failure threshold voltage and the buck conversion circuit 40 and the second rectification circuit 50 work normally, so that the timeliness of power failure detection is improved, the processor 400 can perform data storage operation before power failure, such as data backup of an ammeter and power failure notification sending, in the time when receiving the external interrupt level signal and the terminal voltage of the low-voltage energy storage capacitor 60 is smaller than the working voltage of the system circuit 200 and/or the processor 400, and performs discharge operation of the power failure event by adopting the high-voltage energy storage capacitor 30, so that compared with the single low-voltage energy storage capacitor 60, the data storage time is longer, the data storage is safer, and the working reliability of the electric energy metering device is improved. Moreover, the high-voltage energy storage capacitor 30 is superior to the high-voltage energy storage capacitor 30 in that most of the discharge work of power failure matters is borne, and the low-voltage energy storage capacitor 60 can be of a capacitor structure with smaller capacity and smaller volume, so that the design cost is reduced.
Meanwhile, as shown in fig. 8, the processor 400 adopts an external interrupt input mode to improve the real-time performance of power failure detection, specifically, in the case of power failure, an external interrupt is generated, the processor 400 scans an external interrupt level signal for multiple times, performs filtering to judge whether the power failure is detected, and interrupts and returns when external interference is detected to illegally enter the interrupt or the power failure is not detected, and continues to wait for the external interrupt, and when the power failure is determined, external unnecessary running functional modules in the system circuit 200 are turned off, so that the power load is reduced to the maximum extent, the working time of power failure data storage provided by the high-voltage energy storage capacitor 30 and the low-voltage energy storage capacitor 60 is prolonged to the maximum extent, the safety of power failure data storage is ensured, and after the data storage is completed, the interrupt and return are performed, and other functional operations of the system are continued.
The total duration of the time length of the power-down threshold voltage falling to the working voltage of the switching power supply chip U1 and the time length of the voltage of the low-voltage energy-storage capacitor 60 being lower than the working voltage of the system circuit 200 and/or the processor 400 is the power-down storage time, and the specific required power-down storage time can be determined by setting the power-down threshold voltage, selecting the working voltage of the switching power supply chip U1 of the corresponding model, and the capacitance values of the high-voltage energy-storage capacitor 30 and the low-voltage energy-storage capacitor 60.
For example, when the model of the switching power supply chip U1 is 8235T, the operation start voltage Vsw _ start, the typical value DC40V, and the maximum value DC60V, the voltage when the external ac voltage is supplied in a single phase is derived as:
VAC = Vsw_start/1.414 =60/1.414 = 42.43V；
through the calculation result of the formula, the switching power supply chip U1 with the model 8235T can work normally theoretically when the external alternating voltage single-phase power supply is at the lowest 42.34V, and the minimum working voltage of the external alternating voltage single-phase power supply has little deviation under the influence of peripheral devices, rear-stage output loads and the like.
The rated working voltage of the electric energy metering device comprises AC220V, AC230V, AC110V and the like, the international standard working voltage range of GB, IEC and the like is generally 0.8Un to 1.15Un, and the rated voltage AC220V is taken as an example in the embodiment of the application.
Supposing that the power-down threshold voltage is 79.3V, the rated voltage AC220V and the ultimate lowest working voltage AC110V are far lower than the ultimate working voltage AC110V, the normal work of the electric energy metering device is not influenced, and the power-down threshold voltage is higher than the lowest voltage 42.34V of 8235T switching power supply chip U1 for external alternating voltage single-phase power supply, and the intermediate voltage difference is 79.3-42.34= 36.96V, namely the voltage drop time of 36.96V is still detected after the power-down, so that the power-down storage time is greatly prolonged, the reverse voltage blocking of a diode D17 in the voltage isolation circuit 20 is added, the discharge of high-voltage energy-storage capacitors 30 C2 and C3 is realized, and meanwhile, the power-down storage time is further prolonged by adopting an external interrupted power-down detection method, and the safety of power-down stored metering data is ensured.
Compared with the prior art, the embodiment of the application has the beneficial effects that: the electric energy metering circuit detects the input voltage of the voltage isolation circuit 20, detects power failure in advance when the input voltage is lower than the power failure threshold voltage and the switching power supply works normally, greatly prolongs the power failure data storage time through the high-voltage energy storage capacitor 30, ensures the safety of data storage, can reduce the capacitance value of the low-voltage energy storage capacitor 60 on the premise of ensuring the safety of data storage, reduces the design cost, adopts an external interruption method in a matching manner, can further advance the real-time performance of power failure detection, and ensures the safety of data storage more.
The power-down detection circuit 300 may be formed by a corresponding sampling circuit, a corresponding comparing circuit, and the like, and optionally, as shown in fig. 6, the power-down detection circuit 300 optionally includes:
a voltage sampling circuit 310 connected to the input terminal of the voltage isolation circuit 20, for dividing the input voltage of the voltage isolation circuit 20 and outputting a sampling voltage;
the protection circuit 320 is connected with the output end of the voltage sampling circuit 310 and used for performing voltage protection and filtering;
a voltage detection circuit 330 connected to an output terminal of the protection circuit 320, for comparing the sampling voltage output by the protection circuit 320 with a power-down threshold voltage, and outputting an external interrupt level signal;
the signal isolation circuit 340 is connected with the output end of the voltage detection circuit 330 and is used for performing signal isolation output on the external interrupt level signal;
and a signal conversion circuit 350, connected to the output terminal of the signal isolation circuit 340, for performing signal shaping on the external interrupt level signal and outputting the signal.
In this embodiment, the voltage sampling circuit 310 samples the voltage at the front end of the diode of the voltage isolation circuit 20 and outputs the sampled voltage to the protection circuit 320, the protection circuit 320 protects the voltage detection circuit 330 at the subsequent stage, the voltage detection circuit 330 detects the sampled voltage of the voltage sampling circuit 310 and detects whether the voltage is in a power-down state, when the power-down occurs, the voltage detection circuit 330 controls the voltage isolation circuit 20 to input an external interrupt level signal to the signal conversion circuit 350 and finally to the external interrupt input port of the processor 400, and the processor 400 performs power-down determination and data storage according to the external interrupt level signal.
The voltage sampling circuit 310 may adopt structures such as a sampling resistor and a transformer, the protection circuit 320 may adopt structures such as a clamping circuit and an overvoltage protection circuit 320, for example, a transient diode TVS2 and a fuse, the voltage detection circuit 330 may adopt structures such as a comparator and a switching tube, the signal isolation circuit 340 may adopt isolation circuits such as an optocoupler U4 and a diode, and the signal conversion circuit 350 may adopt a level flip circuit and a level pull-up circuit.
As shown in fig. 7, optionally, the voltage sampling circuit includes a first resistor R23 and a second resistor R24;
the first end of the first resistor R23 forms the input end of the voltage sampling circuit, the second end of the first resistor R23 and the first end of the second resistor R24 are connected to form the output end of the voltage sampling circuit, and the second end of the second resistor R24 is connected with the first grounding end.
The protection circuit 320 includes a transient diode TVS2, a third resistor R25, and a first capacitor C19;
the cathode of the transient diode TVS2 and the first end of the third resistor R25 are connected to the output terminal of the voltage sampling circuit, the second end of the transient diode TVS2 is connected to the first ground terminal, the second end of the third resistor R25 and the first end of the first capacitor C19 are connected together to form the output terminal of the protection circuit 320, and the second end of the first capacitor C19 is connected to the first ground terminal.
The voltage detection circuit 330 includes a first electronic switch Q1;
the first end of the first electronic switch Q1 forms an output end of the voltage detection circuit 330, the second end of the first electronic switch Q1 is connected to the first ground end, and the controlled end of the first electronic switch Q1 forms an input end of the voltage detection circuit 330.
The signal isolation circuit 340 comprises a fourth resistor R26, a fifth resistor R27, an optical coupler U4 and a second capacitor C20;
the first end of fourth resistance R26 and the first end of second electric capacity C20 are connected with positive power source VCC, the second end of fourth resistance R26 is connected with the positive pole of opto-coupler U4's diode, the negative pole of opto-coupler U4's diode constitutes the input of signal isolation circuit 340, the collecting electrode of opto-coupler U4's triode connects the output that constitutes signal isolation circuit 340 with the first end of fifth resistance R27 altogether, the projecting pole and the second earthing terminal of opto-coupler U4's triode are connected, the second end and the source terminal VCC of fifth resistance R27 are connected.
The signal conversion circuit 350 comprises a sixth resistor R28, a seventh resistor R29, a third capacitor C21 and a second electronic switch tube Q2;
a first end of the sixth resistor R28 forms an input end of the signal conversion circuit 350, a second end of the sixth resistor R28 is connected to the controlled end of the second electronic switch Q2, a first end of the seventh resistor R29 and a first end of the third capacitor C21 are connected together to form an output end of the signal conversion circuit 350, a second end of the second electronic switch Q2, a second end of the seventh resistor R29 and a second end of the third capacitor C21 are connected to the second ground end, and a second end of the sixth resistor R28 is connected to the positive power supply VCC.
In the protection circuit 320, the transient diode TVS2 plays a role of clamping voltage to clamp external interference surge voltage, the third resistor R25 and the first capacitor C19 form RC filtering to further eliminate the external interference surge voltage and prevent the voltage detection circuit 330 at the rear stage from being damaged, and the first electronic switching tube Q1 forms the voltage detection circuit 330, wherein the first electronic switching tube Q1 may adopt a structure of a triode, an MOS tube, or the like, optionally, the first electronic switching tube Q1 adopts an NPN triode, a base-emitter PN junction conduction voltage of the NPN triode is near 0.7V, when a power failure occurs, the sampling voltage is lower than 0.7V, the first electronic switching tube Q1 is turned off, and the signal isolation circuit 340 at the rear stage is controlled to act, so as to complete voltage detection.
The signal isolation circuit 340 mainly adopts an optical coupler U4 to complete photoelectric isolation, wherein the processor 400 and the switching power supply circuit 100 are not grounded and need to be subjected to photoelectric isolation to realize the function of power failure detection signal isolation transmission, and the signal conversion circuit 350 is used for performing waveform shaping of power failure signals to improve the recognition degree of an external interrupt input interface of the processor 400.
When the input of an external alternating current power supply is normal, the base voltage of the first electronic switching tube Q1 is greater than 0.7V, the first electronic switching tube Q1 is switched on, the optocoupler U4 is switched on, the second electronic switching tube Q2 receives a low level, the second electronic switching tube Q2 is switched off, and the output power failure detection signal is a high level.
And when power failure occurs, the base voltage of the first electronic switch tube Q1 is less than 0.7V, the first electronic switch tube Q1 is turned off, the optocoupler U4 is turned off, the second electronic switch tube Q2 receives a high level, the second electronic switch tube Q2 is turned on, the power failure detection signal is switched to a low level, the external interrupt input interface of the processor 400 is configured with falling edge input interrupt, and the external interrupt falling edge power failure detection is realized.
The second electronic switching tube Q2 may also adopt a triode or a MOS transistor, such as an NPN triode or an NMOS transistor, and the specific type may be specifically selected according to the requirement, which is not specifically limited herein.
The positive power source VCC may be an internal power source terminal of the system circuit 200, or an output terminal of the second rectifying circuit 50, and may also be an output terminal of the high-voltage energy-storage capacitor 30, where the specific output position is not limited.
The present application further provides an electric energy metering device, which includes an electric energy metering circuit, and the specific structure of the electric energy metering circuit refers to the above-mentioned embodiments, and since the electric energy metering device adopts all the technical solutions of all the above-mentioned embodiments, all the beneficial effects brought by the technical solutions of the above-mentioned embodiments are at least possessed, and are not repeated here.
The electric energy metering device can be an electric energy meter or a concentrator, and the specific structure is not limited.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.
Claims (10)
1. An electric energy metering circuit is characterized by comprising a switching power supply circuit, a power failure detection circuit and a processor;
the switch power supply circuit comprises a first rectifying circuit, a voltage isolating circuit, a high-voltage energy storage capacitor, a voltage reduction conversion circuit, a second rectifying circuit and a low-voltage energy storage capacitor which are connected in sequence, wherein the second rectifying circuit and the low-voltage energy storage capacitor are also connected with a power supply end of a system circuit;
the power failure detection circuit is connected with the input end of the voltage isolation circuit and used for detecting the input voltage of the voltage isolation circuit and outputting an external interrupt level signal when the input voltage is smaller than the power failure threshold voltage;
and the processor is respectively connected with the system circuit and the processor and is used for acquiring a working power supply through the system circuit and carrying out power failure judgment and data storage work after power failure according to the external interrupt level signal.
2. The electric energy metering circuit of claim 1, wherein the step-down conversion circuit comprises a step-down transformer and a switching power supply chip;
and a primary winding of the step-down transformer is respectively connected with a signal end of the switching power supply chip, an output end of the voltage isolation circuit and a power supply end of the high-voltage energy storage capacitor, and a secondary winding of the step-down transformer is connected with an input end of the second rectifying circuit.
3. The electrical energy metering circuit of claim 1, wherein the voltage isolation circuit comprises a diode;
and the anode and the cathode of the diode respectively form the input end and the output end of the voltage isolation circuit.
4. The power metering circuit of claim 1, wherein the power down detection circuit comprises:
the voltage sampling circuit is connected with the input end of the voltage isolation circuit and is used for sampling the input voltage of the voltage isolation circuit in a voltage division mode and outputting the sampling voltage;
the protection circuit is connected with the output end of the voltage sampling circuit and is used for voltage protection and filtering;
the voltage detection circuit is connected with the output end of the protection circuit and used for comparing the sampling voltage output by the protection circuit with the power-down threshold voltage and outputting an external interrupt level signal;
the signal isolation circuit is connected with the output end of the voltage detection circuit and is used for carrying out signal isolation output on the external interrupt level signal;
and the signal conversion circuit is connected with the output end of the signal isolation circuit and is used for shaping and outputting the external interrupt level signal.
5. The power metering circuit of claim 4, wherein the voltage sampling circuit comprises a first resistor and a second resistor;
the first end of first resistance constitutes the input of voltage sampling circuit, the second end of first resistance with the first end of second resistance is connected and is constituted the output of voltage sampling circuit, the second end and the first earthing terminal of second resistance are connected.
6. The electrical energy metering circuit of claim 4, wherein the protection circuit comprises a transient diode, a third resistor, and a first capacitor;
the cathode of the transient diode, the first end of the third resistor and the output end of the voltage sampling circuit are connected, the second end of the transient diode is connected with the first grounding end, the second end of the third resistor and the first end of the first capacitor are connected together to form the output end of the protection circuit, and the second end of the first capacitor is connected with the first grounding end.
7. The electrical energy metering circuit of claim 4, wherein the voltage detection circuit comprises a first electronic switching tube;
the first end of the first electronic switch tube forms the output end of the voltage detection circuit, the second end of the first electronic switch tube is connected with the first grounding end, and the controlled end of the first electronic switch tube forms the input end of the voltage detection circuit.
8. The power metering circuit of claim 4, wherein the signal isolation circuit comprises a fourth resistor, a fifth resistor, an optocoupler, and a second capacitor;
the first end of the fourth resistor and the first end of the second capacitor are connected with a positive power supply end, the second end of the fourth resistor is connected with the anode of the diode of the optocoupler, the cathode of the diode of the optocoupler forms the input end of the signal isolation circuit, the collector of the triode of the optocoupler and the first end of the fifth resistor are connected together to form the output end of the signal isolation circuit, the emitter of the triode of the optocoupler is connected with a second grounding end, and the second end of the fifth resistor is connected with the positive power supply end.
9. The electric energy metering circuit of claim 4, wherein the signal conversion circuit comprises a sixth resistor, a seventh resistor, a third capacitor and a second electronic switching tube;
the first end of the sixth resistor forms an input end of the signal conversion circuit, the second end of the sixth resistor is connected with a controlled end of the second electronic switching tube, the first end of the seventh resistor and the first end of the third capacitor are connected together to form an output end of the signal conversion circuit, the second end of the second electronic switching tube, the second end of the seventh resistor and the second end of the third capacitor are connected with a second grounding end, and the second end of the sixth resistor is connected with a positive power supply end.
10. An electric energy metering device, characterized by comprising the electric energy metering circuit according to any one of claims 1 to 9.
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