Description:TECHNICAL FIELD
[0001] The embodiments of the present disclosure generally relate to electronic electricity meters (e-meters). More particularly, the present disclosure relates to an improved capacitor drop power supply circuits with temperature management mechanism.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] A capacitor drop power supply provides a simple and low cost way for converting an AC voltage such as a mains voltage to a DC supply voltage, which may be used for driving a load. Instead of providing a transformer to step down the voltage, a capacitor (known as a drop capacitor) is coupled in series with the AC supply and acts to step down the voltage. Power supplies of this type are used in various contexts, for example as auxiliary supplies for motor drivers and in electrical appliances.
[0004] Standard electronic electricity meters (e-meters) have traditionally used a capacitive-drop power supply (cap-drop) plus linear regulator topology to provide a cost-effective power supply. Today, opposing forces such as an increase in load currents due to more complex automated meter reading (AMR) and advanced metering infrastructure (AMI) communications circuitry and tighter power consumption regulations, force e-meter designers to limit consumption to below 4VA (~1.2W) for single-phase or 8VA (~2.4W) for 3-phase e-meters
[0005] However, what is a pressing issue with the conventional capacitive-drop power supply (cap-drop) suppose is that, in the present circuit of cap-drop power supply, a single Zener diode is used for voltage regulation. Cap-drop power supply consumes fixed amount of energy at the provided input voltage and irrespective of varying load at output. While load is low, excess energy is dissipated through Zener diode, subsequently increases temperature.
[0006] An illustrative schematic of a typical capacitor drop power supply is shown in FIG. 1. In FIG. 1 the capacitors (C1, C2, C3) limits current due to impedance and a single Zener diode (shown in dotted circle/oval) is used for voltage regulation. A 3 Phase Energy Meter is expected to work from lowest input (single phase available with 120V) and highest input (3Phases available with 288V). Zener voltage value is selected as per lowest input. But, when highest input is available, very large current flows through Zener diode, that generates large amount of heat and raise in temperature. Energy meter enclosure is made of polycarbonate and ultrasonically welded. So, heat generated inside radiates slowly which ultimately reduces life of meter.
[0007] Hence, to summarize the technical problems as recited above, there is a need for a simple, efficient and improved capacitor drop power supply circuits with temperature management mechanism that reduce internal temperature and ultimately helps to increase life of meter.

SUMMARY
[0008] This section is provided to introduce certain objects and aspects of the present invention in a simplified form that are further described below in the detailed description. This summary is not intended to identify the key features or the scope of the claimed subject matter. In order to overcome at least a few problems associated with the known solutions as provided in the previous section, an object of the present disclosure is to provide system, current measuring device and method for noise cancellation and accurate measurement of electric current.
[0009] The invention intends to solve the problem of providing a simple, efficient and improved capacitor drop power supply circuits with temperature management mechanism that reduce internal temperature and ultimately helps to increase life of meter.
[0010] The present invention relates to an improved capacitor drop power supply circuits with temperature management mechanism that uses 3 zener diodes and enables dynamic switching of zener diode to maintain temperature at low level.
[0011] According to the present invention, the 3 zener diodes are used with switching ON and OFF facility through MOSFET.
[0012] MOSFET 1 and MOSFET 2 connected in parallel to at least two zener diodes. MOSFETS are controlled by Microcontroller signals. The microcontroller is loaded with firmware and the firmware periodically calculates voltage of each phase to thereby dynamically switching of zener diode to maintain temperature at low level.
[0013] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The accompanying drawings, which are incorporated herein, and constitute a part of this invention, illustrate exemplary embodiments of the disclosed methods and systems in which like reference numerals refer to the same parts throughout the different drawings. Components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Some drawings may indicate the components using block diagrams and may not represent the internal circuitry of each component. It will be appreciated by those skilled in the art that invention of such drawings includes the invention of electrical components, electronic components or circuitry commonly used to implement such components.
[0015] FIG. 1 illustrates a schematic of a typical capacitor drop power supply with single Zener diode as regulator as know conventionally.
[0016] FIG. 2 illustrates exemplary schematic of a typical capacitor drop power supply with 3 Zener diodes as regulator, according to embodiments of the present disclosure.
[0017] FIG. 3 illustrates exemplary flowchart of firmware that enables dynamic switching of zener diode to maintain temperature at low level, according to embodiments of the present disclosure.
[0018] The foregoing shall be more apparent from the following more detailed description of the invention.

DETAILED DESCRIPTION
[0019] Various example embodiments will now be described more fully with reference to the accompanying drawings in which only some example embodiments are shown. Specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. The present invention, however, may be embodied in many alternate forms and should not be construed as limited to only the example embodiments set forth herein.
[0020] Accordingly, while example embodiments of the invention are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments of the present invention to the particular forms disclosed. On the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of the invention. Like numbers refer to like elements throughout the description of the figures.
[0021] It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments of the present invention. As used herein, the term “and/or,” includes any and all combinations of one or more of the associated listed items.
[0022] It will be understood that when an element is referred to as being “connected,” or “coupled,” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected,” or “directly coupled,” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between,” versus “directly between,” “adjacent,” versus “directly adjacent,” etc.).
[0023] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments of the invention. As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the terms “and/or” and “at least one of” include any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
[0024] It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.
[0025] Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper”, and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, term such as “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein are interpreted accordingly.
[0026] Although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, it should be understood that these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the present invention.
[0027] As recited above, what is a pressing issue with the conventional capacitive-drop power supply (cap-drop) suppose is that, in the present circuit of cap-drop power supply, a single Zener diode is used for voltage regulation. Cap-drop power supply consumes fixed amount of energy at the provided input voltage and irrespective of varying load at output. While load is low, excess energy is dissipated through Zener diode, subsequently increases temperature.
[0028] An illustrative schematic of a typical capacitor drop power supply is shown in FIG. 1. In FIG. 1 the capacitors (C1, C2, C3) limits current due to impedance and a single Zener diode (shown in dotted circle/oval) is used for voltage regulation. A 3 Phase Energy Meter is expected to work from lowest input (single phase available with 120V) and highest input (3Phases available with 288V). Zener voltage value is selected as per lowest input. But, when highest input is available, very large current flows through Zener diode, that generates large amount of heat and raise in temperature. Energy meter enclosure is made of polycarbonate and ultrasonically welded. So, heat generated inside radiates slowly which ultimately reduces life of meter.
[0029] The invention intends to solve the problem of providing a simple, efficient and improved capacitor drop power supply circuits with temperature management mechanism that reduce internal temperature and ultimately helps to increase life of meter.
[0030] The invention intends to solve the problem of providing a simple, efficient and improved capacitor drop power supply circuits with temperature management mechanism that reduce internal temperature and ultimately helps to increase life of meter.
[0031] The present invention relates to an improved capacitor drop power supply circuits with temperature management mechanism that uses 3 zener diodes and enables dynamic switching of zener diode to maintain temperature at low level.
[0032] According to the present invention, the 3 zener diodes are used with switching ON and OFF facility through MOSFET.
[0033] MOSFET 1 and MOSFET 2 connected in parallel to at least two zener diodes. MOSFETS are controlled by Microcontroller signals. The microcontroller is loaded with firmware and the firmware periodically calculates voltage of each phase to thereby dynamically switching of zener diode to maintain temperature at low level.
[0034] FIG. 2 illustrates exemplary schematic of a typical capacitor drop power supply with 3 Zener diodes as regulator, according to embodiments of the present disclosure.
[0035] As shown in FIG. 2, as shown in dotted circle/oval, 3 zener diodes (Z1, Z2 and Z3) are used with switching ON and OFF facility through metal oxide silicon field effect transistors (MOSFET). The MOSFET 1 and MOSFET 2 connected in parallel to Z2 and Z3 respectively. The MOSFETS are controlled by microcontroller signals. Microcontroller is loaded with firmware. Firmware periodically calculates voltage of each phase.
[0036] The implementation of the present invention reduces internal temperature and increases life of meter.
[0037] Consider in prior art (as shown in FIG. 1) there is one Zener of 36V and the present invention with 3 Zener’s of 12 V each. Capdrop impedance is 16K so providing 15 mA DC current at 240V, Threshold 2 is 368 and threshold 1 is 616. 288 Voltage at each phase is highest input. 120V at only one phase and other 2 phases are 0 is lowest input.
Scenario No Individual Voltage Total voltage in Volts Expected current in Zener in mA Voltage of Zener in Volts Maximum possible power dissipation with the arrangement of FIG. 1 in mW No of Zeners ON in Present invention Voltage of each Zener in Volts Maximum possible power dissipation with new method in mW
1) Vr = 288 Vy = 288, Vb = 288 864 54 36 1944 1 12 648
2) Vr = 240 Vy = 240, Vb = 146 616 38.5 36 1386 1 12 462
3) Vr = 240 Vy = 240, Vb = 146 614 38.375 36 1381.5 2 12 921
4) Vr = 240 Vy = 128, Vb = 0 368 23 36 828 2 12 552
5) Vr = 240 Vy = 126, Vb = 0 366 22.875 36 823.5 3 12 823.5
6) Vr = 120 Vy = 0, Vb = 0 120 7.5 36 270 3 12 270

TABLE 1: POWER DISSIPATION WITH THE ARRANGEMENTS


In prior art (FIG. 1) highest power consumption is 1944 and lowest is 270. Whereas, in the present invention the highest value is 921 and the lowest value is 270. Temperature rise inside the meter is in proportion to the power consumption.
Thus, it can be noted from the above facts that the highest value 921 of power consumption of the present invention is much lesser than the power consumption required in prior art of FIG. 1 i.e., 1944. This substantial reduction in the highest power consumptions (from 1944 to 921) reflects/proves the reduction in the internal temperature.
[0038] In an embodiment, a capacitor drop (cap-drop) power supply device for coupling with an input Alternating Current (AC) supply and providing a Direct Current (DC) output voltage is provided. The device includes one or more capacitors.
[0039] In contrast to the conventionally available capacitor drop (cap-drop) power supply devices the device includes at least three Zener diodes (Z1, Z2, Z3) electrically coupled to each of one or more capacitors. The at least two Zener diodes (Z2, Z3) of the at least three Zener diodes (Z1, Z2, Z3) are connected in parallel to at least two metal oxide silicon field effect transistors (MOSFETs) (MOSFET 1, MOSFET 2) such that each of the at least three Zener diodes (Z1, Z2, Z3) are selectively operable and switched to regulate the DC output voltage.
[0040] In an exemplary embodiment, the cap-drop power supply device as claimed in claim 1, wherein the at least three Zener diodes (Z1, Z2, Z3) are configured with switch ON and switch OFF working modes. Each of the switch ON and the switch OFF working modes are controlled by at least on MOSFET of the at least two MOSFETs (MOSFET 1, MOSFET 2).
[0041] In an exemplary embodiment, each of the at least two MOSFETs (MOSFET 1, MOSFET 2) are communicably coupled to one or more microcontrollers, wherein at least one operation of each of the at least two MOSFETs (MOSFET 1, MOSFET 2) is controlled by the one or more microcontrollers.
[0042] In an exemplary embodiment, each of the at least two MOSFETs (MOSFET 1, MOSFET 2) are communicably coupled to one or more microcontrollers, and each of the one or more microcontrollers comprises of a firmware configured to calculate a voltage of each phases of the input Alternating Current (AC) supply to selectively switch and operate, through at least one MOSFET of the at least two MOSFETs, at least one of Zener diode selected from the at least three Zener diodes (Z1, Z2, Z3).
[0043] In an exemplary embodiment, each of the at least two MOSFETs are configured to perform dynamic switching between the at least three Zener diodes (Z1, Z2, Z3) based on a value of the input AC supply.
[0044] FIG. 3 illustrates exemplary flowchart of firmware that enables dynamic switching of zener diode to maintain temperature at low level, according to embodiments of the present disclosure.
[0045] In an exemplary implementation, FIG. 3 shows operations of Zener would be as follows:
Voltage value Vt = Vr+Vy+Vb
Threshold1 = 2Vt/3
Threshold2 = Vt/3
High input: Vt >= Threshold1
Medium input: Vt >= Threshold2 and Vt < Threshold1
Low input = Vt < Threshold2
At high input only Z1 will be active. Due to single Zener low heat dissipation will happen
At Medium input Z1 & Z2 will be active
At Low input Z1, Z2, Z3 will be active. As input is low, very low current will flow through Zener so limited temperature rise.
[0046] Due to the dynamic adjustment of Zener, energy dissipated in Zener is always limited. That prevents rise temperature
[0047] In an embodiment, a method for dynamically switching between at least three Zener diodes (Z1, Z2, Z3) of a capacitor drop (cap-drop) power supply device is disclosed. The method includes the steps of determining values of voltage across each phase of an input Alternating Current (AC) supply; obtaining a total voltage of the input AC supply by adding the determined values of voltage; determining, if the obtained total voltage exceeds a first pre-determined threshold voltage value or is less than a second pre-determined threshold voltage value; and triggering at least one metal oxide silicon field effect transistors (MOSFET) selected from at least two MOSFETs (MOSFET 1, MOSFET 2) based on determination to thereby dynamically switch between the at least three Zener diodes (Z1, Z2, Z3) of the capacitor drop (cap-drop) power supply device.
[0048] In an exemplary embodiment, the method also includes transmitting, by the microcontroller, a switching ON signal to both the at least two MOSFETs (MOSFET 1, MOSFET 2) when the obtained total voltage exceeds a pre-determined threshold voltage value.
[0049] In an exemplary embodiment, the method also includes transmitting, by the microcontroller, a switching OFF signal to both the at least two MOSFETs (MOSFET 1, MOSFET 2) when the obtained total voltage is less than the second pre-determined threshold voltage value.
[0050] In an exemplary embodiment, the method also includes transmitting, by the microcontroller, a switching OFF signal to at least one MOSFET (MOSFET 1) and a switching ON signal to at least one other MOSFET (MOSFET 2) when the obtained total voltage is not less than the second pre-determined threshold voltage value.
[0051] The present disclosure therefore provides various advantages compared with existing capacitor drop power supplies. The various embodiments of the disclosure provide the simplicity and low cost of a capacitor drop power supply, but with an efficiency that is equivalent or superior to that of a switching mode power supply. Furthermore, because extra energy is not dissipated in the power supply of the present disclosure, lower capacitor impedance will not cause extra power loss meaning that the present disclosure allows for the use of low cost capacitive drop techniques with mains supplies that have a high harmonic content.
[0052] What are described above are merely preferred embodiments of the present invention, and are not to limit the present invention; any modification, equivalent replacement and improvement within the principle of the present invention should be included in the protection scope of the present invention.
[0053] The example embodiment or each example embodiment should not be understood as a restriction of the invention. Rather, numerous variations and modifications are possible in the context of the present disclosure, in particular those variants and combinations which can be inferred by the person skilled in the art with regard to achieving the object for example by combination or modification of individual features or elements or method steps that are described in connection with the general or specific part of the description and are contained in the claims and/or the drawings, and, by way of combinable features, lead to a new subject matter or to new method steps or sequences of method steps, including insofar as they concern production, testing and operating methods.
[0054] References back that are used in dependent claims indicate the further embodiment of the subject matter of the main claim by way of the features of the respective dependent claim; they should not be understood as dispensing with obtaining independent protection of the subject matter for the combinations of features in the referred-back dependent claims. Furthermore, with regard to interpreting the claims, where a feature is concretized in more specific detail in a subordinate claim, it should be assumed that such a restriction is not present in the respective preceding claims.
[0055] Since the subject matter of the dependent claims in relation to the prior art on the priority date may form separate and independent inventions, the applicant reserves the right to make them the subject matter of independent claims or divisional declarations. They may furthermore also contain independent inventions which have a configuration that is independent of the subject matters of the preceding dependent claims.
[0056] Further, elements and/or features of different example embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.

[0057] Example embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
, Claims:1. A capacitor drop (cap-drop) power supply device for coupling with an input Alternating Current (AC) supply and providing a Direct Current (DC) output voltage, the device comprising:
one or more capacitors, and
the device characterized by comprising
at least three Zener diodes (Z1, Z2, Z3) electrically coupled to each of one or more capacitors, wherein at least two Zener diodes (Z2, Z3) of the at least three Zener diodes (Z1, Z2, Z3) are connected in parallel to at least two metal oxide silicon field effect transistors (MOSFETs) (MOSFET 1, MOSFET 2) such that each of the at least three Zener diodes (Z1, Z2, Z3) are selectively operable and switched to regulate the DC output voltage.

2. The cap-drop power supply device as claimed in claim 1, wherein the at least three Zener diodes (Z1, Z2, Z3) are configured with switch ON and switch OFF working modes, wherein each of the switch ON and the switch OFF working modes are controlled by at least on MOSFET of the at least two MOSFETs (MOSFET 1, MOSFET 2).

3. The cap-drop power supply device as claimed in claim 1, wherein each of the at least two MOSFETs (MOSFET 1, MOSFET 2) are communicably coupled to one or more microcontrollers, wherein at least one operation of each of the at least two MOSFETs (MOSFET 1, MOSFET 2) is controlled by the one or more microcontrollers.

4. The cap-drop power supply device as claimed in claim 1, wherein each of the at least two MOSFETs (MOSFET 1, MOSFET 2) are communicably coupled to one or more microcontrollers, and each of the one or more microcontrollers comprises of a firmware configured to calculate a voltage of each phases of the input Alternating Current (AC) supply to selectively switch and operate, through at least one MOSFET of the at least two MOSFETs, at least one of Zener diode selected from the at least three Zener diodes (Z1, Z2, Z3).

5. The cap-drop power supply device as claimed in claim 1, wherein each of the at least two MOSFETs are configured to perform dynamic switching between the at least three Zener diodes (Z1, Z2, Z3) based on a value of the input AC supply.

6. A method for dynamically switching between at least three Zener diodes (Z1, Z2, Z3) of a capacitor drop (cap-drop) power supply device as claimed in claim 1, the method comprising:
determining, by a microcontroller, values of voltage across each phase of an input Alternating Current (AC) supply;
obtaining, by the microcontroller, a total voltage of the input AC supply by adding the determined values of voltage;
determining, by the microcontroller, if the obtained total voltage exceeds a first pre-determined threshold voltage value or is less than a second pre-determined threshold voltage value;
trigger, by the microcontroller, based on determination, at least one metal oxide silicon field effect transistors (MOSFET) selected from at least two MOSFETs (MOSFET 1, MOSFET 2) to thereby dynamically switch between the at least three Zener diodes (Z1, Z2, Z3) of the capacitor drop (cap-drop) power supply device.

7. The method as claimed in claim 6, wherein the method includes:
transmitting, by the microcontroller, a switching ON signal to both the at least two MOSFETs (MOSFET 1, MOSFET 2) when the obtained total voltage exceeds a pre-determined threshold voltage value.

8. The method as claimed in claim 6, wherein the method includes:
transmitting, by the microcontroller, a switching OFF signal to both the at least two MOSFETs (MOSFET 1, MOSFET 2) when the obtained total voltage is less than the second pre-determined threshold voltage value.

9. The method as claimed in claim 6, wherein the method includes:
transmitting, by the microcontroller, a switching OFF signal to at least one MOSFET (MOSFET 1) and a switching ON signal to at least one other MOSFET (MOSFET 2) when the obtained total voltage is not less than the second pre-determined threshold voltage value.