Power supply circuit suitable for single-phase high-protection electric energy meter and high-protection intelligent electric meter

Abstract

The utility model provides a power supply circuit suitable for a single-phase high-protection electric energy meter, and a high-protection intelligent electric meter. The power supply circuit comprises an input filtering and rectifying circuit, a step-down circuit, an output rectifying and filtering circuit, a voltage stabilizing circuit, a switch pulse width modulation circuit, and a load voltage feedback circuit. The input filtering and rectifying circuit, the step-down circuit, the output rectifying and filtering circuit and the voltage stabilizing circuit are connected in sequence; the switch pulse width modulation circuit is respectively connected with the input end of the step-down circuit and the load voltage feedback circuit; and the load voltage feedback circuit is also connected with the input end of the voltage stabilizing circuit. A switching power supply scheme is innovatively applied to the single-phase high-protection electric energy meter, and the single-phase high-protection electric energy meter is small in size and light in weight, so that the single-phase high-protection electric energy meter can be easily adapted to a narrow internal space of the single-phase high-protection electric energy meter; and meanwhile, three paths of direct current can be stably output, and the power utilization requirement of an IP68 single-phase high-protection electric energy meter can be well met.

Description

Technical Field

[0001] The utility model relates to the field of electric energy meters, in particular to a power supply circuit suitable for a single-phase high-protection electric energy meter and a high-protection intelligent electric energy meter. Background Art

[0002] The high protection (IP68) smart energy meter is a type of energy meter launched by the State Grid in 2021 to meet the requirements of high protection level. According to GB / T4208-2017 "Enclosure Protection Level (IP) Code", the waterproof and dustproof level of the energy meter is increased from IP54 to IP68. It has all the functions of the corresponding models of the 2020 version of the energy meter. The high protection smart energy meter is mainly designed with four solutions: the bottom shell and the strong current terminal are sealed, the upper shell and the weak current terminal are sealed, the flip cover and the button assembly are sealed, and the upper shell and the bottom shell are sealed, so as to increase the protection of the energy meter to IP68 level.

[0003] Installing high-protection electricity meters in areas prone to floods can increase the reuse rate of electricity meters, reduce the pressure of meter replacement, and speed up the restoration of power to users; installing high-protection electricity meters in high salt fog areas can reduce the risk of rust on the printed circuit boards of electricity meters and increase the service life of the meters.

[0004] In order to meet the requirements of high protection level, the structure of single-phase high protection smart meter has been greatly changed compared with general smart single-phase meter, and its internal space has become smaller. At present, the power supply of smart single-phase meter in China is still mainly based on traditional power frequency transformer, which is heavy and large. Therefore, the previous linear power supply solution is not suitable for single-phase high protection smart energy meter. Utility Model Content

[0005] The technical problem to be solved by the utility model is to provide a power supply circuit and a high-protection intelligent electric meter suitable for a single-phase high-protection electric energy meter, so as to better adapt to the IP68-level high-protection electric energy meter.

[0006] In order to solve the above technical problems, the first technical solution adopted by the utility model is:

[0007] Provide a power supply circuit suitable for a single-phase high-protection electric energy meter, including an input filter and rectifier circuit, a step-down circuit, an output rectifier and filter circuit, a voltage stabilizing circuit, a switch pulse width modulation circuit, and a load voltage feedback circuit;

[0008] The input filtering and rectifying circuit, the step-down circuit, the output rectifying and filtering circuit and the voltage stabilizing circuit are connected in sequence; the switching pulse width modulation circuit is respectively connected to the input end of the step-down circuit and the load voltage feedback circuit; the load voltage feedback circuit is also connected to the input end of the voltage stabilizing circuit.

[0009] Optionally, the output end of the voltage stabilizing circuit is divided into three paths, one path is 12V output, and the other two paths are 5V output.

[0010] Optionally, the 12V output is connected to the MCU module of the electric energy meter after voltage reduction; one 5V output is connected to the metering module of the electric energy meter, and the other 5V output is connected to the 485 communication module of the electric energy meter.

[0011] Optionally, it also includes a protection circuit and a power input terminal; the protection circuit is connected to the power input terminal and the input filter rectifier circuit respectively.

[0012] Optionally, the step-down circuit includes a high-frequency transformer; the high-frequency transformer is provided with three outputs; the three outputs are respectively 12V output, 10V output and 15V output.

[0013] Optionally, the switch pulse width modulation circuit includes a switch pulse width modulation chip, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a capacitor C2, a capacitor C3, a capacitor C4, an electrolytic capacitor E3, a diode DP2 and a diode DP3;

[0014] The resistor R6 and the resistor R7 are connected in series and then connected in parallel with the capacitor C2; one end of the capacitor C2 is respectively connected to the output end of the input filter rectifier circuit and the input end of the step-down circuit, and the other end is connected to the cathode of the diode DP2; the anode of the diode DP2 is respectively connected to the input end of the step-down circuit and the switch pulse width modulation chip; the switch pulse width modulation chip is also grounded via the resistor R8, the capacitor C3 and the capacitor C4 respectively; the non-grounded end of the capacitor C3 is divided into two paths, one is grounded via the electrolytic capacitor E3, and the other is connected to the input end of the step-down circuit via the resistor R9 and the diode DP3 in sequence.

[0015] Optionally, the load voltage feedback circuit includes a resistor R14, a resistor R15, a resistor R16, a resistor R17, a resistor R18, a resistor R22, a capacitor C15, a capacitor C16, an optocoupler and a voltage reference chip; the C pin of the optocoupler is connected to the switch pulse width modulation circuit via the resistor R22; the E pin of the optocoupler is grounded; the K pin of the optocoupler is successively connected to the ground via the resistor R15 and the voltage reference chip; the resistor R14 is connected in parallel between the A pin and the K pin of the optocoupler; The A pin is also connected to the input end of the voltage stabilizing circuit; the A pin of the optocoupler is also connected to the ground via the resistor R16 and the resistor R18 in sequence; the K pin of the voltage reference chip is respectively connected to the resistor R15 and one end of the capacitor C16; the other end of the capacitor C16 is connected to the resistor R18 via the resistor R17; the capacitor C15 is connected in parallel between the capacitor C16 and the resistor R17; the R pin of the voltage reference chip is grounded via the R18; and the A pin of the voltage reference chip is grounded.

[0016] Optionally, the input filtering and rectifying circuit comprises an input filtering unit and an input rectifying unit connected in sequence.

[0017] Optionally, the output rectification and filtering circuit comprises an output rectification unit and an output filtering unit connected in sequence.

[0018] The second technical solution adopted by the utility model is:

[0019] A high-protection smart electric meter comprises the above-mentioned power supply circuit applicable to a single-phase high-protection electric energy meter.

[0020] The beneficial effect of the utility model is that the utility model provides a power supply circuit and a high-protection smart meter suitable for a single-phase high-protection electric energy meter, which uses a switching power supply solution to replace the linear power supply solution used in traditional electric energy meters. Since the switching power supply solution is small in size and light in weight, it is more suitable for IP68 single-phase high-protection electric energy meters with narrow internal space, and can meet the power requirements of IP68 single-phase high-protection electric energy meters. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A circuit module structure and connection diagram of a power supply circuit suitable for a single-phase high-protection electric energy meter provided in an embodiment of the utility model;

[0022] Figure 2 A circuit module structure and connection diagram of a power supply circuit suitable for a single-phase high-protection electric energy meter provided in a specific embodiment of the utility model;

[0023] Figure 3 A schematic diagram of the circuit structure of a power supply circuit suitable for a single-phase high-protection electric energy meter provided in an embodiment of the utility model.

[0024] Description of labels:

[0025] 1. Input filter and rectifier circuit; 2. Buck circuit; 3. Output rectifier and filter circuit;

[0026] 4. Voltage stabilization circuit; 5. Switching pulse width modulation circuit; 6. Load voltage feedback circuit;

[0027] 10. Power input terminal; 20. Protection circuit;

[0028] 100, 485 communication module; 200, metering module; 300, MCU module;

[0029] 11. Input filter unit; 12. Input rectifier unit;

[0030] 31. Output rectification unit; 32. Output filtering unit. DETAILED DESCRIPTION

[0031] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation modes and the accompanying drawings.

[0032] See also Figure 1 , Figure 1 The circuit module structure and connection diagram of the power supply circuit suitable for a single-phase high-protection electric energy meter provided in the embodiment of the utility model. Figure 1 As shown, the present embodiment provides a power supply circuit suitable for a single-phase high-protection electric energy meter, comprising an input filter rectifier circuit 1, a step-down circuit 2, an output rectifier filter circuit 3, a voltage stabilizing circuit 4, a switch pulse width modulation circuit 5, and a load voltage feedback circuit 6. The input filter rectifier circuit 1, the step-down circuit 2, the output rectifier filter circuit 3, and the voltage stabilizing circuit 4 are connected in sequence; the switch pulse width modulation circuit 5 is respectively connected to the input end of the step-down circuit 2 and the load voltage feedback circuit 6; the load voltage feedback circuit 6 is also connected to the input end of the voltage stabilizing circuit 4.

[0033] The input filter rectifier circuit is used to filter out high-frequency interference signals in the input 220V mains power to ensure that the current and voltage flowing into the subsequent circuit are clean and reliable; at the same time, it also converts AC power into DC power;

[0034] The step-down circuit is used to convert the input voltage into a lower voltage;

[0035] The output rectifier and filter circuit is used to convert high-frequency alternating current into direct current and filter out high-frequency interference in the direct current;

[0036] The switch pulse width modulation circuit is used to modulate direct current into high-frequency alternating current of a specific frequency;

[0037] The load voltage feedback circuit is used to change the frequency of the high-frequency alternating current in the switching pulse width modulation circuit according to the voltage at the load end, so as to stabilize the voltage at the load end;

[0038] The voltage stabilizing circuit is used to output direct current with a stable voltage value to power the 485 communication module, the metering module and the MCU module of the single-phase high-protection electric energy meter.

[0039] The power supply circuit suitable for a single-phase high-protection electric energy meter provided in the above-mentioned embodiment applies a switching power supply solution to the single-phase high-protection electric energy meter, thereby solving the problem that the linear power supply solution adopted by the traditional electric energy meter is large and bulky and is not suitable for the single-phase high-protection electric energy meter with a small internal space; since the switching power supply solution is small in size and light in weight, it can be well adapted to the IP68 single-phase high-protection electric energy meter with a small internal space, and can meet the power demand of the IP68 single-phase high-protection electric energy meter.

[0040] In some specific implementations of this embodiment, Figure 2 As shown, the output end of the voltage stabilizing circuit 4 in the above power supply circuit is mainly connected to the 485 communication module 100, the metering module 200 and the MCU module 300 of the single-phase high-protection electric energy meter respectively to supply power to them.

[0041] As a specific example, the output end of the voltage stabilizing circuit is divided into three paths, one of which is 12V output, and the other two are 5V output. Among them, the 12V output is connected to the MCU module of the energy meter after further voltage reduction processing; one of the 5V outputs is connected to the metering module of the energy meter, and the other 5V output is connected to the 485 communication module of the energy meter.

[0042] Here, by designing the output end of the power supply circuit, it is possible to stably output three direct currents of 12V, 5V, and 5V respectively. The above output connection method meets the daily power demand of the IP68 single-phase high-protection electric energy meter and is reasonably designed.

[0043] In some other specific implementations of this embodiment, Figure 2 As shown, the power supply circuit further includes a protection circuit 20 and a power supply input terminal 10; the protection circuit 20 is connected to the power supply input terminal 10 and the input filter rectifier circuit 1 respectively. In other words, the power supply input terminal is connected to the input filter rectifier circuit via the protection circuit. The protection circuit is used to share the voltage and conduct the current in the case of overvoltage and overcurrent, so as to protect the back-end circuit (i.e., the power supply circuit) and play a role in lightning protection and overvoltage protection.

[0044] In some other specific implementations of this embodiment, the step-down circuit in the power supply circuit includes a high-frequency transformer, which is provided with three outputs, each of which is provided with an independent output rectifier and filter circuit; the three outputs are 12V output, 10V output and 15V output, respectively corresponding to the MCU module, 485 communication module and metering module. Here, considering that the metering module is connected to the strong electricity and the 485 communication module has an external terminal, the power supply outputs of these three parts are isolated and three power supplies are used to supply power separately to ensure the stable operation of the MCU module and the safety when it is connected to the strong electricity by mistake.

[0045] See also Figure 3 , Figure 3 The present invention provides a circuit structure diagram of a power supply circuit suitable for a single-phase high-protection electric energy meter. This embodiment is further expanded on the basis of the above embodiment, and each circuit module therein is further refined.

[0046] like Figure 3 As shown, the protection circuit 20 includes a varistor RV1 and a thermistor R1, wherein the varistor RV1 is connected in parallel with the power input terminal N / L; and the thermistor R1 is connected in series with the power input terminal N.

[0047] The input filtering and rectifying circuit comprises an input filtering unit 11 and an input rectifying unit 12 which are connected in sequence.

[0048] The input filter unit 11 includes a filter capacitor C1 and a filter inductor L1; the filter capacitor C1 is connected in parallel with the output of the protection circuit, and the filter inductor L1 is connected in series with the output end of the protection circuit.

[0049] Among them, the input rectifier unit 12 includes a rectifier diode DP1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, an electrolytic capacitor E1 and an electrolytic capacitor E2; the positive electrode of the rectifier diode DP1 is connected to one end of the output end of the input filter unit to form a half-wave rectifier circuit; the resistors R2, R3, R4 and R5 are connected in series in sequence and connected in parallel as a whole to the negative electrode of the rectifier diode DP1 and the other end of the output end of the input filter unit; the electrolytic capacitor E1 and the electrolytic capacitor E2 are connected in series and connected in parallel as a whole to the negative electrode of the rectifier diode DP1 and the other end of the output end of the input filter unit.

[0050] The step-down circuit includes a high-frequency transformer TR1; the high-frequency transformer TR1 is provided with one input and three outputs; the three outputs are 12V output, 10V output and 15V output respectively.

[0051] The switch pulse width modulation circuit 5 includes a switch pulse width modulation chip U3, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a capacitor C2, a capacitor C3, a capacitor C4, an electrolytic capacitor E3, a diode DP2 and a diode DP3. The resistor R6 and the resistor R7 are connected in series and connected in parallel with the capacitor C2. One end of the capacitor C2 is connected to the cathode of the diode DP2, and the other end is connected to the input end of the high-frequency transformer TR1. The anode of the diode DP2 is also connected to the input end of the high-frequency transformer TR1 to form a freewheeling circuit. The 5th to 8th pins of the switch pulse width modulation chip U3 are connected and then connected to the anode of the diode DP2; the 1st pin is connected to the resistor R8 and then grounded; the 2nd pin is directly grounded; the 3rd pin is respectively connected to the capacitor C3 and the electrolytic capacitor E3 and then grounded; the 3rd pin is also connected to the cathode of the diode DP3 via the resistor R9, and the cathode of the diode DP3 is connected to the input end of the high-frequency transformer TR1; the 4th pin (FB pin) is connected to the capacitor C4 and then grounded.

[0052] The output rectifying and filtering circuit includes an output rectifying unit 31 and an output filtering unit 32 which are connected in sequence.

[0053] The output rectifier unit 31 includes a resistor R11, a resistor R12, a resistor R10, a capacitor C7, an electrolytic capacitor E5, a capacitor C11, an electrolytic capacitor E6, a capacitor C5, an electrolytic capacitor E4, a diode DP4, a diode DP5 and a diode DP6. The resistor R11 and the capacitor C7 are connected in series and then connected in parallel with the diode DP5; the positive electrode of the diode DP5 is connected to the output terminal 8 pin of the high-frequency transformer TR1, and the negative electrode is connected to the positive electrode of the electrolytic capacitor E5, and the negative electrode of the electrolytic capacitor E5 is connected to the output terminal 9 pin of the high-frequency transformer TR1; the resistor R12 and the capacitor C11 are connected in series and then connected in parallel with the diode DP6, the positive electrode of the diode DP6 is connected to the output terminal 13 pin of the high-frequency transformer TR1, the negative electrode is connected to the positive electrode of the electrolytic capacitor E6, and the positive electrode of the electrolytic capacitor E6 is connected to the output terminal 14 pin of the high-frequency transformer TR1; the resistor R10 and the capacitor C5 are connected in series and then connected in parallel with the diode DP4, the positive electrode of the diode DP4 is also connected to the output terminal 1 pin of the high-frequency transformer TR1, the negative electrode is connected to the positive electrode of the electrolytic capacitor E4, and the negative electrode of the electrolytic capacitor E4 is grounded.

[0054] The output filter unit 32 includes an inductor L2, a capacitor C12, an electrolytic capacitor E7, a capacitor C14, and a resistor R13. The capacitor C12 is connected in parallel with the electrolytic capacitor E6 in the output rectifier unit; the non-grounded end of the capacitor C12 is also connected to the positive electrode of the electrolytic capacitor E7 via the inductor L2; the negative electrode of the electrolytic capacitor E7 is grounded; the capacitor C14 and the resistor R13 are connected in parallel with the electrolytic capacitor E7 respectively.

[0055] The load voltage feedback circuit 6 includes a resistor R14 , a resistor R15 , a resistor R16 , a resistor R17 , a resistor R18 , a resistor R22 , a capacitor C15 , a capacitor C16 , an optical coupler, and a voltage reference chip. One end of the resistor R14 is respectively connected to the load voltage end (i.e., the non-grounded end of the capacitor C12 in the above-mentioned output filter unit) and the A pin of the optocoupler; the other end of the resistor R14 is respectively connected to one end of the resistor R15 and the K end of the optocoupler; the other end of the resistor R15 is connected to the K pin of the voltage reference chip; after the resistor R16 is connected in series with the resistor R18, the end of the resistor R16 not connected to the resistor R18 is connected to the A end of the optocoupler, and the end of the resistor R16 connected to the resistor R18 is also connected to the R pin of the voltage reference chip; the end of the resistor R18 not connected to the resistor R16 is grounded; the capacitor C16 and the resistor R17 are connected in series as a whole and connected in parallel with the capacitor C15, and then one end of the whole is connected to the K pin of the voltage reference chip, and the other end is connected to the R pin of the voltage reference chip; the A pin of the voltage reference chip is grounded; the E pin of the optocoupler is grounded, and the C pin is connected to the resistor R22 and then connected to the FB pin of the switch pulse width modulation chip U3 in the switch pulse width modulation circuit. Here, the rectified and filtered voltage output by the buck circuit is divided by resistors R16 and R18 and given to the voltage reference chip. The voltage reference chip uses this to control the channel of the optocoupler and provide a feedback signal for the switching pulse width modulation circuit.

[0056] The voltage stabilizing circuit 4 includes a resistor R116, a resistor R19, a resistor R20, a resistor R21, a capacitor C18, a capacitor C19, a capacitor C22, a capacitor C23, a capacitor C24, a capacitor C25, an electrolytic capacitor E8, an electrolytic capacitor E9, a voltage stabilizing chip U6 and a diode DP7. After capacitor C18 and capacitor C19 are connected in parallel, one end of the whole is connected to pin 6 of the voltage stabilizing chip U6, and the other end is grounded; after capacitor C22 and electrolytic capacitor E8 are connected in parallel, one end of the whole is connected to pin 4 of the voltage stabilizing chip U6, and the other end is grounded; one end of resistor R116 is connected to pin 5 of the voltage stabilizing chip U6, and the other end is grounded; after resistor R19 and resistor R20 are connected in series, one end of the whole is connected to pin 4 of the voltage stabilizing chip U6, and the other end is connected to pin 3 of the voltage stabilizing chip U6; one end of resistor R21 is connected to pin 3 of the voltage stabilizing chip U6, and the other end is grounded; capacitor C23, capacitor C24, and electrolytic capacitor E9 are connected in parallel to pin 1 and pin 2 of the voltage stabilizing chip U6, respectively; the positive electrode of diode DP7 is connected to pin 1 of the voltage stabilizing chip U6, and the negative electrode is connected to one end of capacitor C25; the other end of capacitor C25 is grounded; pin 2 of the voltage stabilizing chip U6 is grounded.

[0057] In this embodiment, the 220V AC mains power is connected from the power input terminal, first passes through the protection circuit, and then enters the input filter unit to filter out the interference signal in the mains power, ensuring that the mains power flowing into the back-end circuit is clean and reliable; then enters the input rectifier unit to convert it into DC power; then enters the switch pulse width modulation circuit to modulate it into a high-frequency AC power with a specific frequency pulse width; then it is subjected to a step-down process by the step-down circuit to obtain three power outputs, which are used for the power supply of the 485 communication module, the metering module, and the MCU module respectively; but the power signal flowing out of the step-down circuit is not stable, and it needs to be processed by subsequent circuits before it can be used for actual power supply. Specifically, the three outputs of the step-down circuit will successively pass through the output rectifier unit and the output filter unit to obtain three low-voltage DC signals with interference signals filtered out and stable voltage, and these three low-voltage DC signals are 12V, 10V, and 15V respectively; the low-voltage DC signal then passes through the voltage stabilizing circuit to output three stable DC power. Specifically, the 12V low-voltage DC signal is converted to a stable 12V and 5.7V through the voltage stabilization circuit, which is used to power the carrier and MCU (12V is used for the external carrier module, and 5.7V is used for the MCU module); the 10V low-voltage DC signal and the 15V low-voltage DC signal are converted to two stable 5V through the voltage stabilization circuit, which are used for the 485 communication module and the metering module respectively. In addition, the voltage flowing out of the step-down circuit will also be given to the load voltage feedback circuit, which will change the frequency of the high-frequency AC modulated by the switch pulse width modulation circuit according to the voltage change at the load end, so as to stabilize the voltage at the load end and better meet the power demand of the single-phase high-protection smart meter.

[0058] An embodiment of the present invention further provides a high-protection smart meter, which includes a power supply circuit suitable for a single-phase high-protection electric energy meter as described in any of the above embodiments. Among the three outputs of the power supply circuit, the 12V output is connected to the MCU module of the electric energy meter after further stepping down to 5.7V; one 5V output is connected to the metering module of the electric energy meter, and the other 5V output is connected to the MCU of the 485 communication module of the electric energy meter.

[0059] In summary, the power supply circuit and high-protection smart meter provided by the utility model are suitable for single-phase high-protection electric energy meters, which can solve the problem that the linear power supply solution used in traditional electric energy meters cannot be applied to IP68 single-phase high-protection electric energy meters due to its large size and bulkiness. The switching power supply solution is innovatively applied to the IP68 single-phase high-protection electric energy meter. Since the switching power supply circuit is small in size and light in weight, it can be easily placed in a single-phase high-protection electric energy meter with a small internal space; at the same time, it can stably output three-way direct current, which well meets the power demand of the IP68 single-phase high-protection electric energy meter.

[0060] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent transformations made using the contents of the specification and drawings of the present invention, or directly or indirectly applied in the relevant technical field, are also included in the patent protection scope of the present invention.

Claims

1. Suitable for the power supply circuit of single-phase high protection electric energy meter, characterized in that: It includes an input filtering and rectifying circuit, a voltage-reducing circuit, an output rectifying and filtering circuit, a voltage-stabilizing circuit, a switching pulse width modulation circuit, and a load voltage feedback circuit; The input filtering and rectifying circuit, the step-down circuit, the output rectifying and filtering circuit and the voltage stabilizing circuit are connected in sequence; the switching pulse width modulation circuit is respectively connected to the input end of the step-down circuit and the load voltage feedback circuit; the load voltage feedback circuit is also connected to the input end of the voltage stabilizing circuit.

2. The power supply circuit suitable for a single-phase high-protection electric energy meter as claimed in claim 1, characterized in that: The output end of the voltage stabilizing circuit is divided into three paths, one path is 12V output, and the other two paths are 5V output.

3. The power supply circuit suitable for a single-phase high-protection electric energy meter as claimed in claim 2, characterized in that: The 12V output is connected to the MCU module of the electric energy meter after voltage reduction; one 5V output is connected to the metering module of the electric energy meter, and the other 5V output is connected to the 485 communication module of the electric energy meter.

4. The power supply circuit suitable for a single-phase high-protection electric energy meter as claimed in claim 1, characterized in that: It also includes a protection circuit and a power input terminal; the protection circuit is connected to the power input terminal and the input filtering and rectifying circuit respectively.

5. The power supply circuit suitable for a single-phase high-protection electric energy meter as claimed in claim 1, characterized in that: The step-down circuit includes a high-frequency transformer; the high-frequency transformer is provided with three outputs; the three outputs are respectively 12V output, 10V output and 15V output.

6. The power supply circuit suitable for a single-phase high-protection electric energy meter as claimed in claim 1, characterized in that: The switch pulse width modulation circuit includes a switch pulse width modulation chip, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a capacitor C2, a capacitor C3, a capacitor C4, an electrolytic capacitor E3, a diode DP2 and a diode DP3; The resistor R6 and the resistor R7 are connected in series and then connected in parallel with the capacitor C2; one end of the capacitor C2 is respectively connected to the output end of the input filter rectifier circuit and the input end of the step-down circuit, and the other end is connected to the cathode of the diode DP2; the anode of the diode DP2 is respectively connected to the input end of the step-down circuit and the switch pulse width modulation chip; the switch pulse width modulation chip is also grounded via the resistor R8, the capacitor C3 and the capacitor C4 respectively; the non-grounded end of the capacitor C3 is divided into two paths, one is grounded via the electrolytic capacitor E3, and the other is connected to the input end of the step-down circuit via the resistor R9 and the diode DP3 in sequence.

7. The power supply circuit suitable for a single-phase high-protection electric energy meter as claimed in claim 1, characterized in that: The load voltage feedback circuit includes a resistor R14, a resistor R15, a resistor R16, a resistor R17, a resistor R18, a resistor R22, a capacitor C15, a capacitor C16, an optical coupler and a voltage reference chip; the C pin of the optical coupler is connected to the switch pulse width modulation circuit via the resistor R22; the E pin of the optical coupler is grounded; The K pin of the optocoupler is connected to ground via the resistor R15 and the voltage reference chip in turn; the resistor R14 is connected in parallel between the A pin and the K pin of the optocoupler; the A pin of the optocoupler is also connected to the input end of the voltage stabilizing circuit; the A pin of the optocoupler is also connected to ground via the resistor R16 and the resistor R18 in turn; the K pin of the voltage reference chip is respectively connected to the resistor R15 and one end of the capacitor C16; the other end of the capacitor C16 is connected to the resistor R18 via the resistor R17; the capacitor C15 is connected in parallel between the capacitor C16 and the resistor R17; the R pin of the voltage reference chip is grounded via R18; the A pin of the voltage reference chip is grounded.

8. The power supply circuit suitable for a single-phase high-protection electric energy meter as claimed in claim 1, characterized in that: The input filtering and rectifying circuit comprises an input filtering unit and an input rectifying unit which are connected in sequence.

9. The power supply circuit suitable for a single-phase high-protection electric energy meter as claimed in claim 1, characterized in that: The output rectifying and filtering circuit comprises an output rectifying unit and an output filtering unit which are connected in sequence.

10. High protection smart meter, characterized by: A power supply circuit suitable for a single-phase high-protection electric energy meter comprising the power supply circuit described in any one of claims 1 to 8.

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