DESC:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to analog-to-digital converters (ADC), employing a voltage reference,and more particularly,to a closed loop system for maintaining voltage reference constant against variations such load, temperature drift and the like.

BACKGROUND

[002] Traditionally known industrial products uses analog to digital convertor (ADC) to perform critical parameter measurement.The ADC converts an input voltage VIN into an electric digital signal by comparing the input VIN with a voltage reference VREF. The voltage reference VREF may be externally provided to the ADC or may be internally generated by the ADC. In case of internal reference, internal voltage of a device or microcontroller (MCU) is used as reference voltage and in case of an external reference; external voltage is supplied as a reference voltage. The voltage reference VREF is intended to be precise against which the input voltage VIN is compared. As such, the voltage reference VREF has to be precise in order for the ADC to accurately convert a given input voltage VIN into a digital signal. Any error in ADC measurement may produce an error in the device or equipment used, and thus may result in the degradation of performance of the device or equipment.

[003] The ADC reference voltage Vref plays a major role in accuracy of the ADC as the conversion of input voltage VIN depend upon the reference value used for the ADC. Any change in Vref will affect the ADC measurement and simultaneously will affect the product accuracy and performance. ADC conversion formula is as follows

[004] The error in reference voltages Vref used in ADC causes a difference in the actual value and conversion value. Some of the error in reference voltage Vref is due to variation in component value as the ADC count value will be different for each value even though the component lies within the range and due to temperature drift (variation)there is variation in the reference voltage and hence the reference voltage gives different conversion results at different temperatures even for the same input value.

[005] The prior art document, US8736469 B2 discloses a method and system for minimizing variation of converter voltage reference wherein a voltage reference generator generates a voltage reference from a supply voltage, wherein the voltage reference is fed to an analog to digital convertor which generates an output signal based on an input signal and the voltage reference from the voltage reference generator.

[006] The prior art document, US20130162259 A1 discloses a system and method for developing highly accurate measurements by calibrating monitoring units with the known accurate measurements of reference voltages of an adjacent monitoring unit and further comparing the two measurements of the reference voltage and a correction factor is calculated to be used to correct subsequent measurements from the adjacent monitoring packs.

[007] The prior art document, US 20090146857 A1 discloses a voltage source providing a constant reference voltage, independent of load variations at an output terminal. The effective impedance (looking-in impedance) at the output terminal is designed to be independent of frequency of the signals at the output terminal. In an embodiment, the resistance of one of two parallel impedance paths constituting the effective impedance is made equal to the resistance of the other path, and the time constants of both paths are made equal. As a result, the effective impedance is made independent of frequency, and the strength of the reference voltage is maintained constant without exhibiting ringing, DC droop, etc., despite load variations.

[008] The prior art document, US 4957074 A discloses Closed loop electric valve control for internal combustion engine. The actual lift of a valve is monitored by a lift sensor that is coupled to an electronic valve controller by a lift signal processing circuit, and the electronic valve controller issues a control signal that is calculated to secure as faithful correspondence as possible of this lift signal to a command signal that the electronic valve controller receives from an electronic engine management controller. The processing circuit functions to disclose to the electronic valve controller the actual opening and closing instants of the valve in a manner that amounts to the sensor being precisely re-calibrated each time that it closes.

[009] The prior art document, US 6664852 B2 wherein an apparatus and method for controlling an output of a digital system comprising, for example, an output of a power amplifier to minimize or neutralize nonlinearities such as limit cycles. The digital system comprises a nonlinearity means or limit cycle suppressor to counter the limit cycle effect by intentionally introducing a second nonlinearity into the system to suppress the limit cycle effect in the digital system.

[0010] The prior art document, US 7154331 B2 wherein a method and apparatus relating to current and gain adjustment in an amplifier is disclosed. A gain of an amplifier, e.g., closed loop gain, may be increased or decreased based on a swing of a received signal. A current of an internal amplifier stage may be increased or decreased in relation to the increasing or decreasing of the gain to provide adjustments to bandwidth and/or frequency response. In one embodiment a programmable gain amplifier having operational amplifier has a variable feedback resistor increased/decreased in steps and a bias current of a differential stage of the operational amplifier may be increased/decreased in proportional steps.

[0011] The existing techniques to maintainthe reference voltage in ADC systems are open loop systems and thus there is no provision to compensate the change in reference voltage due temperature drifts, component value variation and the like. Hence, there exists a need to provide a more accurateclosed loop system to maintain the reference voltage by monitoring any change in the reference voltage and subsequently adjusting the change of the reference voltage so as to maintain a constant reference voltage in ADC system.

SUMMARY OF THE INVENTION

[0012] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[0013] The main object of the present invention is to provide a closed loop system maintaining a constant reference voltage in analog to digital convertors.

[0014] Another object of the present invention is to provide a closed loop system for compensating the change in reference voltage due to error such as temperature drift, change component value and the like.

[0015] Accordingly, the present invention provides a closed loop system for maintaining a constant reference voltage Vref in an analog to digital convertors (ADCs) and subsequently compensating any change in Vref due to prevailing error such as temperature drift, change in component value and the like.

[0016] In one implementation, the present invention a close loop system for maintaining analog to digital convertor (ADC) voltage reference Vrefwherein the reference voltage in ADC is generated using a voltage generator. The output of the voltage generator is fed to ADC as a reference voltage wherein the voltage generator further comprises a feedback component that is configured to modify the reference voltage or the output voltage of the voltage generator.

[0017] In one implementation, the present invention provides a method to compensate any change in reference voltage wherein the method comprises generating a reference voltage using a voltage generator, monitoring the change in reference voltage by using ADC component, measuring the change in the reference voltage by using controller to read the output of ADC and compare it with a pre-set to determine the change, compensating the change in reference voltage in the voltage generator by using feedback component.

[0018] In one implementation, a close loop system is currently not used in any conventional ADC applications, they have open loop system for measurement. The conventional systems only consist of voltage reference and analog to digital converters. The present invention provides close loop system in which no calibration is required as the mechanism in present invention itself tune it to match the ideal levels required for operation. It is well known that, the passive components do change their characteristics as per temperature. Changes in this parameter of the components will affect the voltage reference generated. ADC will monitor the changes happened in the voltage reference and accordingly it well set the DAC value. The output of DAC is connected to digital potentiometer which will adjust itself to tune the voltage reference level. The offset due to component tolerance will be adjusted to meet the desired reference level.Normally in production calibration process is performed to remove the offset due to component tolerance. This system is a self-tuning system hence it will adjust itself to match the desired output hence calibration require to meet this performance is not required. Eliminating calibration process will reduce the time to produce the device as well as costly equipment to use to calibrate the devices in production is not required. Their cost will be saved with improving production output. Further, the close loop system as disclosed in the present invention reduces error in the measurement and improves the product performance. Further, the present invention may be also used to If any component failure happens in the measurement section then it will provide the impact on reference voltage generated. For an example if power supply fails then in result it will fail the reference voltage as it will be derived from the power supply. Then the ADC values for the reference voltage will goes out of band and reference failure will be declared for the system.

[0019] Accordingly, in one implementation, a close loop analog to digital converts (ADC) reference maintenance system, The system comprises at least one voltage generator configured to generate at least one reference voltage (Vref) based on at least one feedback circuitry; at least one analog to digital converter (ADC) configured to receive the reference voltage and measure a value of the Vref to thereby monitor the change in the value of Vref; at least one controller configured to receive the value of Vref and compare the value of Vref with at least one required value pre-stored, wherein if the value of Vref and the required value pre-stored are not identical, the controller is further configured to generate at least one value in accordance with the required value pre-stored; at least one digital to analog converter (DAC) configured to receive the value in accordance with the required value pre-stored generated by the controller and thereby control the generation of the reference voltage (Vref).

[0020] In one implementation, the method for voltage reference maintenance in a system, the method comprises:
· generating, by at least one voltage generator, at least one reference voltage (Vref) based on at least one feedback circuitry;
· receiving, by at least one analog to digital converter (ADC), the reference voltage;
· measuring, by the analog to digital converter (ADC), a value of the Vref;
· monitoring, by the analog to digital converter (ADC), the change in the value of Vref;
· receiving, by at least one controller configured, the value of Vref;
· comparing, by the controller, the value of Vref with at least one required value pre-stored, wherein if the value of Vref and the required value pre-stored are not identical;
· generating, by controller, at least one value in accordance with the required value pre-stored;
· receiving, by at least one digital to analog converter (DAC), the value in accordance with the required value pre-stored generated by the controller;
· controlling, by the digital to analog converter (DAC), the generation of the reference voltage (Vref).

[0021] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0022] Figure 1 illustratesa block diagram representation for close loop ADC reference system,in accordance with an embodiment of the present subject matter.

[0023] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0024] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0025] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0026] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0027] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0028] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0029] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0030] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0031] Referring now to figure 1, a block diagram representation of a close loop system for maintaining analog to digital convertor voltage reference is illustrated. In one implementation, the close loop system for maintaining analog to digital convertor voltage reference includes a voltage generator, an analog to digital convertor (ADC), a microcontroller, a digital to analog convertor (DAC) as feedback component. The present invention provides addition of Digital to analog converter (DAC) for monitoring of ADC voltage reference in the system. This component of the present invention enables the system to function/work as a self-tuning system.

[0032] In one implementation, the voltage generator may be of any kind of regulatory output provider such as LDO or DC to DC converts, in all voltage generators feedback pin is present to monitor the output voltage generated. In the present invention the voltage is controlled at this feedback pin using a DAC output. The output of voltage generator may be feed to ADC and the ADC may convert this voltage level to discrete value and then this discrete value may be compared with the desired value for voltage level. Depending upon the difference between desired value and actual value DAC counts may be set. External factors like temperature, component tolerance impacts can be corrected using this system. As the changes due to this factors may be tuned by the system, the component tolerance results into offset levels for the system. This offset level introduces fixed error in measurement. This offset may be positive or negative depends upon the component tolerance. Initially (i.e. before self-tuning) ADC may read the voltage reference and theremay be difference between desired value and actual value this difference is mostly due to offset error. Using DAC this voltage generator feedback may be adjusted to achieve the desired reference level. For the temperature variation the voltage reference value may drift as per the ambient temperature, the ADC may continuously monitor the voltage reference value andany distinctive drift of voltage reference may be identified based on which the DAC value may be adjusted to get the desired reference value.

[0033] In one implementation, a single channel in the selected ADC is required to measure Vref value from the voltage generator and monitors the change in the reference value. The ADC is connected to a microcontroller to read the reference value using a ADC so as to perform a control logic.

[0034] In one implementation, the controller measure the ADC value and then it verifies the value with a preset value and in case the output value of ADC exceeds the preset value, the microcontroller enables the DAC to compensate the change in voltage. The DAC output accordingly to reset the required voltage value in the voltage generator.

[0035] In one implementation, the DAC is a digital to analog converter. DACis configured to receive a command from the microcontroller so as to set the output value accordingly to control the reference voltage.

[0036] Some of the important features of the present invention, considered to be noteworthy are mentioned below:
1. The present invention enables Vref monitoring for temperature drift or any change in Vref.
2. The present invention provides a close loop system that gives more reliability of the reference voltage.
3. Error reduction in result improves the system or product performance.
4. The present invention eliminates calibration need for a product. As system will be a self-tuning system.
,CLAIMS:1. A close loop analog to digital converts (ADC) reference maintenance system, comprising:
at least one voltage generator configured to generate at least one reference voltage (Vref) based on at least one feedback circuitry;
at least one analog to digital converter (ADC) configured to receive the reference voltage and measure a value of the Vref to thereby monitor the change in the value of Vref;
at least one controller configured to receive the value of Vref and compare the value of Vref with at least one required value pre-stored, wherein if the value of Vref and the required value pre-stored are not identical, the controller is further configured to generate at least one value in accordance with the required value pre-stored;
at least one digital to analog converter (DAC) configured to receive the value in accordance with the required value pre-stored generated by the controller and thereby control the generation of the reference voltage (Vref).

2. The close loop Analog to Digital converts (ADC) reference maintenance system as claimed in claim 1, wherein the feedback circuitry comprises an adjustable low drop output (LDO) regulator with a variable resistor, wherein the variable resistor is adjustable based on the value generated by the DAC to control the generation of the reference voltage (Vref).

3. The close loop Analog to Digital converts (ADC) reference maintenance system as claimed in claim 1, wherein the ADC comprises at least one channel to measure Vref value.

4. A method for voltage reference maintenance in a system, the method comprising:
generating, by at least one voltage generator, at least one reference voltage (Vref) based on at least one feedback circuitry;
receiving, by at least one analog to digital converter (ADC), the reference voltage;
measuring, by the analog to digital converter (ADC), a value of the Vref;
monitoring, by the analog to digital converter (ADC), the change in the value of Vref;
receiving, by at least one controller configured, the value of Vref;
comparing, by the controller, the value of Vref with at least one required value pre-stored, wherein if the value of Vref and the required value pre-stored are not identical;
generating, by controller, at least one value in accordance with the required value pre-stored;
receiving, by at least one digital to analog converter (DAC), the value in accordance with the required value pre-stored generated by the controller;
controlling, by the digital to analog converter (DAC), the generation of the reference voltage (Vref).