Method and system for calculating electrical properties of an electric heater

Abstract

A method for controlling a temperature of a heater including a resistive heating element includes measuring a voltage count and a current count based on data from an analog-to-digital converter (ADC) circuit of a sensor circuit electrically connected to the heater, the method includes selecting one or more dynamic gain levels for the ADC from among a plurality of dynamic gain levels based on a shift gain correlation, determining a resistance value of the resistive heating element based on the voltage count, the current count, and the one or more dynamic gain levels, and controlling power to the heater based on the resistance value.

Description

[Technical field]

[0001] cross reference This application claims priority to and the benefit of U.S. Provisional Application No. 63 / 250,655, filed September 30, 2021, the disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to the calculation of electrical properties of electric heaters. [Background technology]

[0003] The discussion herein is merely intended to provide background information related to the present disclosure and may not constitute prior art.

[0004] A thermal system generally includes a heater having a resistive heating element and a control system that controls power to the heater to generate heat at a temperature setpoint. In one application, a semiconductor processing system includes a thermal system having a pedestal heater, the pedestal heater including a heating plate having a ceramic substrate and one or more resistive heating elements that define one or more heating zones. Summary of the Invention [Problem to be solved by the invention]

[0005] In some applications, the heater may be a "two-wire" heater, where the resistive heating element has two leads instead of four operatively connected to the heating element and functions as both a heater and a temperature sensor. A control system configured to control the heater determines a temperature of the resistive heating element based on a resistance value of the resistive heating element. Specifically, the control system calculates a resistance value based on a voltage measurement and / or a current measurement, and determines a temperature of the resistive heating element based on the calculated resistance value. Typically, the voltage and current measurements are calibrated to accurately determine resistance values ​​at various temperature setpoints, and resistance-temperature correlation data is used to determine a temperature based on the calculated resistance value. However, it may be difficult to obtain accurate resistance measurements and corresponding temperature measurements over a particular power or temperature range.

[0006] This section provides a general summary of the disclosure, but does not comprehensively disclose its entire scope or all features. [Means for solving the problem]

[0007] The present disclosure provides a method of controlling a temperature of a heater including a resistive heating element, the method including measuring a voltage count and a current count based on data from an analog-to-digital converter (ADC) circuit of a sensor circuit electrically connected to a heater, the method including selecting one or more dynamic gain levels for the ADC from among a plurality of dynamic gain levels based on a shift gain correlation, determining a resistance value of the resistive heating element based on the voltage count, the current count, and the one or more dynamic gain levels, and controlling power to the heater based on the resistance value.

[0008] The following includes variations on the method of controlling the heater temperature in the above paragraph, which may be implemented individually or in any combination.

[0009] In one embodiment, the one or more dynamic gain levels include a voltage dynamic gain level, a current dynamic gain level, or a combination thereof. In one embodiment, the method further includes determining a voltage value based on a ratio of the voltage count to the voltage dynamic gain level and determining a current value based on a ratio of the current count to the current dynamic gain level, wherein the resistance value of the resistive heating element is further based on the voltage value and the current value. In one embodiment, selecting the one or more dynamic gain levels based on the shift gain correlation further includes determining whether the voltage count is greater than a voltage shift down threshold while the ADC selects a predetermined voltage dynamic gain level from among the plurality of dynamic gain levels, and selecting the voltage dynamic gain level less than the predetermined voltage dynamic gain level as the one or more dynamic gain levels in response to the voltage count being greater than the voltage shift down threshold. In one form, selecting the one or more dynamic gain levels based on the shift gain correlation further includes determining whether the voltage count is less than a voltage shift up threshold while the ADC is selecting a predetermined voltage dynamic gain level from among the plurality of dynamic gain levels, and selecting the voltage dynamic gain level greater than the predetermined voltage dynamic gain level as the one or more dynamic gain levels in response to the voltage count being less than the voltage shift up threshold.

[0010] In one embodiment, selecting the one or more dynamic gain levels based on the shift gain correlation further includes determining whether the current count is greater than a current shift down threshold while the ADC is selecting a predetermined current dynamic gain level from among the plurality of dynamic gain levels, and selecting the current dynamic gain level less than the predetermined current dynamic gain level as the one or more dynamic gain levels in response to the current count being greater than the current shift down threshold.In one embodiment, selecting the one or more dynamic gain levels based on the shift gain correlation further includes determining whether the current count is less than a current shift up threshold while the ADC is selecting a predetermined current dynamic gain level from among the plurality of dynamic gain levels, and selecting the current dynamic gain level greater than the predetermined current dynamic gain level as the one or more dynamic gain levels in response to the current count being less than the current shift up threshold.

[0011] In one embodiment, the method further includes determining a plurality of voltage null counts and a plurality of current null counts when the heater is not powered, the resistance value being further based on the plurality of voltage null counts and the plurality of current null counts. In one embodiment, each of the plurality of voltage null counts is associated with one of the plurality of dynamic gain levels, and each of the plurality of current null counts is associated with one of the plurality of dynamic gain levels. In one embodiment, the method further includes determining a voltage value based on a difference between the voltage count and a predetermined voltage null count of the plurality of voltage null counts, and determining a current value based on a difference between the current count and a predetermined current null count of the plurality of current null counts, the resistance value of the resistive heating element being further based on the voltage value and the current value. In one embodiment, the method further includes determining a plurality of voltage drift counts and a plurality of current drift counts, the resistance value being further based on the plurality of voltage drift counts and the plurality of current drift counts.

[0012] The present disclosure provides a system for controlling a temperature of a heater including a resistive heating element. The system comprises one or more processors configured to execute instructions stored on a non-transitory computer readable medium. The instructions include obtaining data from an analog-to-digital converter (ADC) circuit of a sensor circuit electrically connected to a heater, measuring a voltage count and a current count based on the data, and selecting a voltage dynamic gain level and a current dynamic gain level for the ADC from among a plurality of dynamic gain levels based on a shift gain correlation. The instructions include determining a resistance value of the resistive heating element based on the voltage count, the current count, the voltage dynamic gain level, and the current dynamic gain level, and controlling power to the heater based on the resistance value.

[0013] The following includes variations of the heater temperature control system in the above paragraph, which may be implemented individually or in any combination.

[0014] In one embodiment, the instructions further include determining a voltage value based on a ratio of the voltage count to the voltage dynamic gain level and determining a current value based on a ratio of the current count to the current dynamic gain level, the resistance value of the resistive heating element being further based on the voltage value and the current value. In one embodiment, the instructions for selecting the voltage dynamic gain level based on the shift gain correlation further include determining whether the voltage count is greater than a voltage shift down threshold while the ADC is selecting a predetermined voltage dynamic gain level from among the plurality of dynamic gain levels, and selecting the voltage dynamic gain level less than the predetermined voltage dynamic gain level in response to the voltage count being greater than the voltage shift down threshold. In one embodiment, the instructions for selecting the voltage dynamic gain level based on the shift gain correlation further include determining whether the voltage count is less than a voltage shift up threshold while the ADC is selecting a predetermined voltage dynamic gain level from among the plurality of dynamic gain levels, and selecting the voltage dynamic gain level greater than the predetermined voltage dynamic gain level in response to the voltage count being less than the voltage shift up threshold.

[0015] In one form, the instructions for selecting a current dynamic gain level based on the shift gain correlation further include determining whether the current count is greater than a current shift down threshold while the ADC is selecting a predetermined current dynamic gain level from among the plurality of dynamic gain levels, and selecting the current dynamic gain level less than the predetermined current dynamic gain level in response to the current count being greater than the current shift down threshold.In one form, the instructions for selecting a current dynamic gain level based on the shift gain correlation further include determining whether the current count is less than a current shift up threshold while the ADC is selecting a predetermined current dynamic gain level from among the plurality of dynamic gain levels, and selecting the current dynamic gain level greater than the predetermined current dynamic gain level in response to the current count being less than the current shift up threshold.

[0016] In one form, the instructions further include determining a plurality of voltage null counts and a plurality of current null counts when the heater is not powered, the resistance value being further based on the plurality of voltage null counts and the plurality of current null counts. In one form, each of the plurality of voltage null counts is associated with one of the plurality of dynamic gain levels, and each of the plurality of current null counts is associated with one of the plurality of dynamic gain levels. In one form, the instructions further include determining a voltage value based on a difference between the voltage count and a predetermined voltage null count of the plurality of voltage null counts, and determining a current value based on a difference between the current count and a predetermined current null count of the plurality of current null counts, the resistance value of the resistive heating element being further based on the voltage value and the current value. In one form, the instructions further include determining a plurality of voltage drift counts and a plurality of current drift counts, the resistance value being further based on the plurality of voltage drift counts and the plurality of current drift counts.

[0017] Further areas of applicability will become apparent from the description provided herein. It should be understood that the specification and specific examples are for purposes of illustration only and are not intended to limit the scope of the present disclosure. [Brief description of the drawings]

[0018] In order that the present disclosure may be better understood, various forms thereof will now be described, by way of example only, with reference to the accompanying drawings in which:

[0019] [Figure 1A] FIG. 1 is a block diagram of a thermal system having an electrical properties calculator in accordance with the teachings of the present disclosure.

[0020] [Figure 1B] FIG. 1B is a block diagram of a control system for the thermal system of FIG. 1A.

[0021] [Diagram 2] 13 is a graph illustrating a resistance curve determined without dynamic gain shifting in accordance with the teachings of the present disclosure.

[0022] [Diagram 3] 1 is a graph illustrating a resistance curve determined using dynamic gain shifting in accordance with the teachings of the present disclosure.

[0023] [Figure 4] 13 is a graph illustrating temperature curves determined without dynamic gain shifting in accordance with the teachings of the present disclosure.

[0024] [Diagram 5] 13 is a graph illustrating a temperature curve determined using dynamic gain shifting in accordance with the teachings of the present disclosure.

[0025] [Figure 6A] 11 is a flowchart illustrating an example calibration routine for one or more dynamic gain levels in accordance with the teachings of the present disclosure.

[0026] [Figure 6B] 5 is a flow chart illustrating another example calibration routine in accordance with the teachings of the present disclosure.

[0027] [Figure 6C] 4 is a flow chart illustrating an exemplary electrical resistance calculation routine in accordance with the teachings of the present disclosure.

[0028] [Figure 6D] 5 is a flow chart illustrating another example electrical resistance calculation routine in accordance with the teachings of the present disclosure.

[0029] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The following description is merely exemplary in nature and is in no way intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0031] 1A and 1B, the thermal system 100 includes a multi-zone pedestal heater 102 and a control system 104. The control system 104 includes a controller 106 and a power converter system 108. In one embodiment, the heater 102 includes a heating plate 110 and a support shaft 112 disposed on a bottom surface of the heating plate 110. The heating plate 110 includes a substrate 111 and a plurality of resistive heating elements (not shown) embedded in the substrate 111 or disposed along a surface of the substrate 111. In one embodiment, the substrate 111 can be made of ceramic or aluminum. The control system 104 independently controls the resistive heating elements, which define a plurality of heating zones 114, as shown by the dashed lines in FIG. 1A. It should be understood that the heating zones may be configured in various manners and may include any number of heating zones while remaining within the scope of the present disclosure. Additionally, although the controller 106 is described in connection with a multi-zone heater, the heater 102 may include one or more zones and is not limited to two or more zones.

[0032] In one form, the heater 102 is a "two-wire" heater in which two leads, rather than four, are operatively connected to the resistive heating element, such that the resistive heating element functions both as a heater and as a temperature sensor. Such two-wire functionality is disclosed, for example, in U.S. Pat. No. 7,196,295, which is commonly assigned with this application and is incorporated by reference in its entirety. Typically, in a two-wire system, the resistive heating element is defined by a material whose resistance changes with changes in temperature such that the average temperature of the resistive heating element is determined based on the change in resistance of the resistive heating element. In one embodiment, the resistance of the resistive heating element is calculated by first measuring the voltage across and current through the heating element, and then using Ohm's law to determine the resistance.

[0033] The control system 104 controls the operation of the heater 102, and more particularly, independently controls the power supplied to each zone 114. In one form, the control system 104 is electrically connected to the zones 114 via terminals 115 such that each zone 114 is connected to two terminals that supply power and sense temperature.

[0034] In one aspect, control system 104 is communicatively connected (e.g., via wireless and / or wired communications links) to a computing device 117 having one or more user interfaces such as a display, keyboard, mouse, speakers, touch screen, among others. Using computing device 117, a user can provide inputs or commands to thermal system 100, such as temperature setpoints, power setpoints, and commands to execute tests or processes stored by control system 104.

[0035] The control system 104 is electrically connected to a power source 118 that provides an input voltage (e.g., 240V, 208V) to the power converter system 108 via an interlock 120. The interlock 120 controls power flow between the power source 118 and the power converter system 108 and is operable by the controller 106 as a safety mechanism to cut off power from the power source 118. Although illustrated in FIG. 1A, the control system 104 may not include the interlock 120 in other variations.

[0036] In one embodiment, the power converter system 108 regulates the input voltage and provides an output voltage (V OUT ) to the resistive heating elements of a given zone 114 (114-1 to 114-N in the figures). In one form, the power converter system 108 includes a plurality of power converters 122 (122-1 to 122-N in FIG. 1B) configured to apply adjustable power to the resistive heating elements of a given zone 114 (114-1 to 114-N in the figures). One example of such a power converter system is described in U.S. Pat. No. 10,690,705, which is commonly owned with this application and the contents of which are incorporated herein by reference in their entirety. In this embodiment, each power converter system 108 includes a step-down converter operable by a controller to generate a desired output voltage for one or more heating elements of a given zone 114. Thus, the power converter system 108 is operable to provide a customizable amount of power (i.e., a desired power) to each zone 114 of the heater 102. It should be readily understood that other power converter systems may be employed to provide the desired power, and the present disclosure is not limited to the examples provided herein.

[0037] With the use of a two-wire heater (such as heater 102), the control system 104 includes sensor circuits 124 (i.e., 124-1 through 124-N in FIG. 1B) for measuring the electrical properties (i.e., voltage and / or current) of the resistive heating elements used to determine resistance and temperature. In one form, each sensor circuit 124 includes an ammeter 126 and a voltmeter 128 to measure the current through and the voltage applied to the heating element in a given zone 114, respectively. In one form, the ammeter 126 and voltmeter 128 are provided as power measurement chips that simultaneously measure current and voltage regardless of the power applied to the heating element.

[0038] In one form, the controller 106 includes one or more microprocessors and a memory for storing computer readable instructions executed by the microprocessor. In one embodiment, the controller 106 is configured to execute one or more control processes in which the controller 106 determines a desired power to be applied to the heater 102, such as 100% of the input voltage, 90% of the input voltage, etc. The desired power may be determined based on various information, such as, but not limited to, the electrical characteristics of the heater (e.g., voltage, current, and / or resistance), the temperature of the heater, the operating state of the heater (e.g., soft start, ramp-up, steady state, ramp-down, etc.), and / or the desired set points (e.g., temperature set point, ramp-up rate set point, ramp-down rate set point, power set point, etc.). Examples of control processes are described in the above-mentioned U.S. Pat. No. 10,690,705 and commonly owned U.S. Pat. No. 10,908,195, the contents of which are incorporated herein by reference in their entireties. In one embodiment, the controller 106 implements a closed loop temperature control in which the temperature of the heater 102 is controlled to a temperature setpoint.

[0039] An electric heater (such as heater 102) may not use the entire range of operating power (i.e., voltage and / or current) during operation, and heater 102 may use more power during ramp-up or set point changes than when maintaining heater 102 at a desired temperature. Thus, heater 102 may be operated primarily at the lower end of a power band. At the lower end of the power band, resistance measurements, and therefore temperature measurements, become less accurate, thereby making the electric heater difficult to control. Thus, controller 106 may include an Electrical Characteristic Calculator (ECC) 130 configured to improve the accuracy of resistance value determinations performed by controller 106. Specifically, ECC 130 is configured to read voltage and current counts (i.e., VI counts) and determine the resistance of the resistive heating element of heater 102 based on the VI counts. Further details regarding ECC 130 are provided below.

[0040] In one embodiment, the sensor circuit 124 includes an analog-to-digital converter (ADC) configured to measure voltage (e.g., peak or root-mean-square (RMS) voltage at the ADC's power supply or sense terminals) and current (e.g., peak or RMS current measured across a shunt resistor). Voltage and current may hereinafter be collectively referred to as "VI." In one form, the ADC generates counts, which are integer representations of millivolt (mV) input signal levels, typically 12, 16, or 24-bit values. In a non-limiting example, the ADC, which is a 24-bit device, generates count values ​​in the range of 0 to 16,777,215 (±8,388,607). Typically, using calibration data, the sensor circuit 124 converts the VI counts into actual voltage and current measurements. In lieu of actual voltage and current measurements, the ECC 130 determines a resistance value (R) based on the ratio of the voltage and current values. As shown in the following equation (1), the voltage value is expressed as the voltage count (V Counts ) and voltage dynamic gain level (V Gain ) and the current value is based on the ratio of current counts (ICounts ) and current dynamic gain level (I Gain ) ratio. R = (V Counts / V Gain )) / (I Counts / I Gain )) (1)

[0041] The determined resistance value is therefore a unitless value that is independent of the calibration accuracy of the sensor circuit 124. The ADC current dynamic gain level and the ADC voltage dynamic gain level are hereinafter collectively referred to as "dynamic gain level", and further details regarding the ADC dynamic gain level are provided below.

[0042] In one form, the ADC may have a fixed gain such that the entire operating range (i.e., power range) of the product may be measured. The fixed gain may reduce the accuracy of the resistance measurement at low power levels, so the full measurement range of the ADC is typically not or rarely utilized. Therefore, the ECC 130 is configured to ignore the fixed gain when determining the resistance value of the resistive heating element of the heater 102 and select one or more dynamic gain levels for the ADC.

[0043] In one embodiment, the ADC includes a programmable gain amplifier (PGA) for selecting / adjusting one or more dynamic gain levels among a plurality of dynamic gain values ​​of the ADC. As an example, the PGA includes six selectable voltage dynamic gain levels and six selectable current dynamic gain levels, such as 1, 2, 4, 8, 16, etc., and the PGA is configured to independently adjust / select the voltage dynamic gain levels and the current dynamic gain levels. It should be understood that the voltage dynamic gain levels and the current dynamic gain levels may be set to be non-independent of each other. Dynamically adjusting the gain of the ADC improves the fidelity of the VI counts and resistance measurements, which in turn improves the resistance-based control routine of the heater 102, as described in more detail below.

[0044] In one form, the ADC selects the dynamic gain levels based on a shift gain correlation that correlates each dynamic gain level with a shift up threshold and a shift down threshold (collectively referred to hereinafter as "shift thresholds"). In one form, the shift thresholds are provided as threshold counts for increasing or decreasing the dynamic gain levels. The ADC selects the shift thresholds such that there is substantially no overlap after a shift in the dynamic gain levels and sufficient headroom (i.e., hysteresis) after the shift.

[0045] As an example, the voltage count (V Counts ) is greater than the voltage shift down threshold, the ADC Gain ) (e.g., V Counts When V is greater than the voltage shift down threshold of 16,000,000 counts, the ADC Gain (V Counts ) is less than the voltage shift up threshold, the ADC Gain ) (e.g., V Counts When V is less than the voltage shift up threshold of 4,000,000 counts, the ADC Gain to a predetermined voltage dynamic gain level of 4 to 8). It should be understood that the downshift threshold and upshift threshold are merely examples and should not be limited to these examples set forth herein.

[0046] As a further example, the current count (I Counts ) is greater than the current shift-down threshold, the ADC shifts the current dynamic gain level (I Gain ) (e.g., I Counts When I is greater than the current shift-down threshold of 8,000,000 counts, the ADC Gain(I Counts ) is less than the current shift up threshold, the ADC shifts the current dynamic gain level (I Gain ) (e.g., I Counts When I is less than the current shift up threshold of 2,000,000 counts, the ADC Gain to a predetermined current dynamic gain level of 4 to 8). Although examples of various dynamic gain levels and shift thresholds are provided, it should be understood that various dynamic gain levels are associated with various VI counts and shift thresholds and are not limited to the examples provided herein.

[0047] In one embodiment, the ECC 130 is configured to employ a stabilization delay in response to the ADC decreasing or increasing at least one of the current dynamic gain level and the voltage dynamic gain level. In one embodiment, the stabilization delay is based on the settling time of the ADC (i.e., the amount of time to converge to a final count value) or is arbitrary. As an example, when the ECC 130 adjusts the current (or voltage) dynamic gain level, the ECC 130 does not start taking VI counts until the stabilization delay has elapsed. As another example, when the ECC 130 adjusts the current (or voltage) dynamic gain level, the ECC 130 discards VI counts obtained before the stabilization delay period has elapsed. By employing a stabilization delay when adjusting the dynamic gain level, the ECC 130 can further improve the accuracy of the VI counts. It should be understood that a stabilization delay may not be employed in some embodiments.

[0048] In one aspect, the ECC 130 is configured to adjust the VI count based on a plurality of voltage null counts and a plurality of current null counts (collectively referred to hereinafter as "Null Counts"). More specifically, the ECC 130 is configured to perform a count compensation determination to determine the VI count when the voltage and current are zero (i.e., no power is being applied to the heater 102). As an example, for each dynamic gain level, with power off, the count compensation determination reads and stores the VI count from the ADC as a null count for the respective dynamic gain level (i.e., a current null count for each current dynamic gain level and a voltage null count for each voltage dynamic gain level). The ECC 130 is configured to use the null counts to correct the measurement counts during operation and measure the resistance value (R) as shown in the following relations (2)-(4). V Comp-counts = V Counts -V Null-counts (2) I Comp-counts = I Counts -I Null-counts (3) R = (V Comp-counts / V Gain ) / (I Comp-counts / I Gain ) (4)

[0049] In the formula (2), "V Null-counts ” is the voltage null count determined during count compensation determination for the given voltage dynamic gain level being employed, and “V Comp-counts " is the compensated voltage count (i.e., the difference between the voltage count and the corresponding voltage null count). In relation (3), "I Null-counts ” is the current null count determined during count compensation determination of the current dynamic gain level employed, and “I Comp-counts" is the compensated current count (i.e., the difference between the current count and the corresponding current null count). As shown in relation (4), the ECC 130 determines a voltage value based on the ratio of the compensated voltage value to the corresponding voltage dynamic gain level being employed, determines a current value based on the ratio of the compensated current value to the corresponding current dynamic gain level being employed, and determines a resistance value based on the voltage value and the current value.

[0050] In one embodiment, the ECC 130 is configured to determine the resistance value based on a plurality of voltage drift counts and a plurality of current drift counts (collectively referred to hereinafter as "drift counts"). The drift counts represent induced voltage count error and / or current count error at a given temperature due to, for example, performance degradation and / or aging associated with the sensor circuit 124 (e.g., the power measurement chip of the controller 106), the power converter 122, and other components of the control system 104. As an example, when applying power to increase the temperature of the resistive heating element of the heater 102 based on a heater temperature setpoint, thereby increasing the temperature of the sensor circuit 124 by, for example, 50° C. (i.e., 100 voltage counts / 1° C.), the measured voltage count may be 5,000 counts less (or greater) than the actual voltage count. As another example, when power is applied to increase the temperature of the resistive heating element of the heater 102 based on the heater temperature setpoint, thereby increasing the temperature of the sensor circuit 124 by, for example, 50° C. (i.e., 200 current counts / 1° C.), the measured current count may be 10,000 counts greater (or less) than the actual current count. Thus, the ECC 130 is configured to perform a drift current count compensation determination for each current dynamic gain level and a drift voltage count compensation determination for each voltage dynamic gain level to determine the drift counts.

[0051] To determine the current drift count, the ECC 130 is adapted to determine the difference between the compensated current count (or current count) determined by the ADC and an expected current count corresponding to sensor data output by a separate reference temperature sensor (not shown) proximate (i.e., adjacent and / or nearby) to a power measurement chip, voltage divider, current shunt, or other measurement component having a known (or empirically defined) count value per Celsius / Fahrenheit, where the reference temperature sensor is configured to generate data indicative of a temperature proximate to or of the measurement component itself. To determine the voltage drift count, the ECC 130 is adapted to determine the difference between the compensated voltage count (or voltage count) determined by the ADC and an expected voltage count corresponding to sensor data output by another reference sensor proximate to or of the measurement component itself, where the reference temperature sensor is configured to generate data indicative of a temperature proximate to or of the measurement component itself. In some forms, the ECC 130 periodically updates the drift count to further improve the accuracy of the compensated voltage count and / or current count. It should be understood that in some forms, drift counts may not be employed.

[0052] 2-5 are graphs illustrating features of the method performed by the ECC 130 of the present disclosure. More specifically, FIGS. 2 and 3 are graphs illustrating VI counts and resistance curves in which resistance values ​​are calculated without and with dynamic gain shifting, respectively. As shown in FIG. Counts and I Counts are limited to approximately 1,000,000 and 2,000,000, respectively, and the calculated resistance (i.e., the Load Resistance) overlaps with the Filtered Resistance, but still fluctuates. With dynamic gain shift (Figure 3), V Counts and I Counts have been expanded to approximately 6 million and 5 million respectively. Counts and I CountsBy increasing the fidelity of the V, the calculated resistance value becomes smoother and closer to the filtered resistance value. At a fixed gain, the full measurement range of the PGA is not utilized. Therefore, the ECC130 uses a V Counts and I Counts The optical amplifier may further be configured to include a dynamic gain shift that adjusts the gains of the optical amplifiers independently of one another.

[0053] By improving the accuracy of the resistance value, the control improves the accuracy of the temperature. Specifically, Figures 4 and 5 respectively show the temperature and PID effort curves without dynamic gain shifting (i.e., FilamentTemp1, FilamentTemp2 in Figure 4) and with dynamic gain shifting (i.e., FilamentTemp1, FilamentTemp2 in Figure 5). When applying dynamic gain shifting, the filament temperature curve is smoother and closer to the temperature detected by the reference sensor (i.e., TcRefSensor1), thereby improving the control routine based on the resistance or temperature associated with the heater 102.

[0054] 6A-6B, an exemplary calibration routine executed by the control system 104 is provided. FIG. 6A illustrates a calibration routine 200 that may be implemented at cold start, before power is applied to the heater 102. At 202, the ECC 130 determines and stores a null count, as described in more detail above. For example, the ECC 130 may determine and store a null count when no power is applied to the heater 102, and in some variations, for each available dynamic gain level. Counts and I Counts6B illustrates a calibration routine 210 performed by the ECC 130 to account for induced voltage and / or current count errors of the sensor circuit 124 at a given temperature. At 212, the control system 104 supplies a known amount of power to the resistive heating element of the heater 102 for each dynamic gain level of the ADC. At 214, the ECC 130 determines and stores a drift count based on the difference between the expected VI count and the determined VI count, as described in more detail above.

[0055] 6C, an exemplary resistance calculation routine 240 is shown that may be implemented as part of another control program, such as a steady state control or ramp down control, to determine the resistance of the resistive heating element of the heater 102. At 242, the ECC 130 calculates V Counts and I Counts At 244, the ECC 130 selects a dynamic gain level based on the shift gain correlation, and at 246, the ECC 130 reads V Counts , I Counts , and V Counts and I Counts The controller 106 determines a resistance value based on a dynamic gain level associated with the resistance value. The controller 106 employs the determined resistance value to control the heater 102 (e.g., control the power applied to the heater 102) according to the master control program employed.

[0056] 6D, an exemplary resistance calculation routine 250 is shown that may be implemented as part of another control program, such as a steady state control or ramp down control, to determine the resistance of the resistive heating element of the heater 102. At 252, the ECC 130 calculates V Counts and I Counts At 254, the ECC 130 selects a dynamic gain level based on the shift gain correlation, and at 256, the ECC 130 reads V Counts , I Counts , V Counts and I Countsand at least one of the null count (e.g., the null count determined by the calibration routine 210 illustrated in FIG. 6A) and the drift count (e.g., the null count determined by the calibration routine 220 illustrated in FIG. 6B). The controller 106 employs the determined resistance value to control the heater 102 (e.g., to control the power applied to the heater 102) in accordance with the main control program employed.

[0057] It should be readily understood that the routines may be provided in a variety of suitable manners and should not be limited to the routines of Figures 6A-6D For example, the routines may include a calibration scaling routine to account for offsets inherent in the thermal system.

[0058] In one form, the ECC 130 is configured to determine the resistance value based on the VI counts for various operating powers of the heater 102. In another form, the ECC 130 is configured to calculate the resistance value based on the VI counts when the power to the electric heater (as the heater 102) is below a certain threshold (e.g., 5% input power), and when the power is above the certain threshold, the ECC 130 reads calibrated voltage and current values ​​from the sensor circuit 124 and employs the calibrated values ​​to determine the resistance value.

[0059] Unless otherwise stated herein, all numerical values ​​expressing mechanical / thermal properties, compositional percentages, dimensions and / or tolerances, or other characteristics are to be understood as being modified by the word "about" or "approximately" in describing the scope of the present disclosure. This modification may be desirable for a variety of reasons, including industrial practices, materials, manufacturing, assembly tolerances, and testing capabilities.

[0060] In this specification, the expression "at least one of A, B, and C" should be interpreted as meaning a logical non-exclusive OR (A OR B OR C), and should not be interpreted as meaning "at least one of A, at least one of B, and at least one of C."

[0061] In this application, the term "controller" may be interchangeable with the term "circuitry." The term "controller" may refer to, be a part of, or include the following: an application specific integrated circuit (ASIC), digital, analog, or mixed analog / digital discrete circuitry, a digital, analog, or mixed analog / digital integrated circuit, a combinatorial logic circuit, a field programmable gate array (FPGA), a processor circuit (shared, dedicated, or group) that executes code, a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit, other suitable hardware components that provide the described functionality, or a system on a chip, any or all of the above.

[0062] The term code includes software, firmware, and / or microcode, and may refer to programs, routines, functions, classes, data structures, and / or objects. The term memory circuits is a subset of the term computer-readable medium. As used herein, the term computer-readable medium does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as on a carrier wave), and thus the term computer-readable medium is considered to be tangible and non-transitory.

[0063] The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the essence of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as departing from the spirit and scope of the disclosure.

Claims

1. 1. A method of controlling the temperature of a heater including a resistive heating element, comprising: measuring voltage counts and current counts based on data from an analog-to-digital converter circuit in a sensor circuit electrically connected to the heater; selecting one or more dynamic gain levels for the analog-to-digital converter circuit from among a plurality of dynamic gain levels based on a shift-gain correlation; determining a resistance value of the resistive heating element based on a first ratio of the voltage count to one of the one or more dynamic gain levels and a second ratio of the current count to one of the one or more dynamic gain levels; controlling power to the heater based on the resistance value; A method comprising:

2. The method of claim 1 , wherein the one or more dynamic gain levels include a voltage dynamic gain level, a current dynamic gain level, or a combination thereof.

3. determining a voltage value based on the first ratio of the voltage count to the voltage dynamic gain level; determining a current value based on the second ratio between the current count and the current dynamic gain level; further comprising The method of claim 2 , wherein the resistance value of the resistive heating element is further based on a third ratio of the voltage value to the current value.

4. selecting the one or more dynamic gain levels based on the shift-gain correlation further comprises: determining whether the voltage count is greater than a voltage downshift threshold while the analog-to-digital converter circuit is selecting a predetermined voltage dynamic gain level from among the plurality of dynamic gain levels; selecting the voltage dynamic gain level less than the predetermined voltage dynamic gain level as the one or more dynamic gain levels in response to the voltage count being greater than the voltage shift down threshold; The method of claim 2 , comprising:

5. selecting the one or more dynamic gain levels based on the shift-gain correlation further comprises: determining whether the voltage count is less than a voltage shift-up threshold while the analog-to-digital converter circuit is selecting a predetermined voltage dynamic gain level from among the plurality of dynamic gain levels; selecting the voltage dynamic gain level greater than the predetermined voltage dynamic gain level as the one or more dynamic gain levels in response to the voltage count being less than the voltage upshift threshold; The method of claim 2 , comprising:

6. selecting the one or more dynamic gain levels based on the shift-gain correlation further comprises: determining whether the current count is greater than a current downshift threshold while the analog-to-digital converter circuit is selecting a predetermined current dynamic gain level from among the plurality of dynamic gain levels; selecting the current dynamic gain level less than the predetermined current dynamic gain level as the one or more dynamic gain levels in response to the current count being greater than the current downshift threshold; The method of claim 2 , comprising:

7. selecting the one or more dynamic gain levels based on the shift-gain correlation further comprises: determining whether the current count is less than a current shift-up threshold while the analog-to-digital converter circuit is selecting a predetermined current dynamic gain level from among the plurality of dynamic gain levels; selecting the current dynamic gain level greater than the predetermined current dynamic gain level as the one or more dynamic gain levels in response to the current count being less than the current upshift threshold; The method of claim 2 , comprising:

8. 2. The method of claim 1, further comprising determining a plurality of voltage null counts and a plurality of current null counts when no power is supplied to the heater, and wherein the resistance value is further based on the plurality of voltage null counts and the plurality of current null counts.

9. each of the plurality of voltage null counts is associated with one of the plurality of dynamic gain levels; The method of claim 8 , wherein each of the plurality of current null counts is associated with one of the plurality of dynamic gain levels.

10. determining a voltage value based on a difference between the voltage count and a predetermined voltage null count of the plurality of voltage null counts; determining a current value based on a difference between the current count and a predetermined current null count of the plurality of current null counts; further comprising The method of claim 8 , wherein the resistance value of the resistive heating element is further based on the voltage value and the current value.

11. The method of claim 1 , further comprising determining a plurality of voltage drift counts and a plurality of current drift counts, wherein the resistance value is further based on the plurality of voltage drift counts and the plurality of current drift counts.

12. 1. A system for controlling the temperature of a heater including a resistive heating element, comprising: one or more processors configured to execute instructions stored on a non-transitory computer-readable medium; The instruction: acquiring data from an analog-to-digital converter circuit of a sensor circuit electrically connected to the heater; measuring voltage counts and current counts based on said data; selecting a voltage dynamic gain level and a current dynamic gain level for the analog-to-digital converter circuit from among a plurality of dynamic gain levels based on the shift gain correlation; determining a resistance value of the resistive heating element based on a first ratio of the voltage count to the voltage dynamic gain level and a second ratio of the current count to the current dynamic gain level; controlling power to the heater based on the resistance value; Including, the system.

13. The instructions further include: determining a voltage value based on the first ratio of the voltage count to the voltage dynamic gain level; determining a current value based on the second ratio between the current count and the current dynamic gain level; Including, 13. The system of claim 12, wherein the resistance value of the resistive heating element is further based on a third ratio of the voltage value to the current value.

14. the instructions for selecting the voltage dynamic gain level based on the shift gain correlation include: determining whether the voltage count is greater than a voltage downshift threshold while the analog-to-digital converter circuit is selecting a predetermined voltage dynamic gain level from among the plurality of dynamic gain levels; selecting the voltage dynamic gain level less than the predetermined voltage dynamic gain level in response to the voltage count being greater than the voltage downshift threshold; The system of claim 12 further comprising:

15. the instructions for selecting the voltage dynamic gain level based on the shift gain correlation include: determining whether the voltage count is less than a voltage shift-up threshold while the analog-to-digital converter circuit is selecting a predetermined voltage dynamic gain level from among the plurality of dynamic gain levels; selecting the voltage dynamic gain level greater than the predetermined voltage dynamic gain level in response to the voltage count being less than the voltage upshift threshold; The system of claim 12 further comprising:

16. the instructions for selecting the current dynamic gain level based on the shift gain correlation include: determining whether the current count is greater than a current downshift threshold while the analog-to-digital converter circuit is selecting a predetermined current dynamic gain level from among the plurality of dynamic gain levels; selecting the current dynamic gain level less than the predetermined current dynamic gain level in response to the current count being greater than the current downshift threshold; The system of claim 12 further comprising:

17. the instructions for selecting the current dynamic gain level based on the shift gain correlation include: determining whether the current count is less than a current shift-up threshold while the analog-to-digital converter circuit is selecting a predetermined current dynamic gain level from among the plurality of dynamic gain levels; selecting the current dynamic gain level greater than the predetermined current dynamic gain level in response to the current count being less than the current upshift threshold; The system of claim 12 further comprising:

18. 13. The system of claim 12, wherein the instructions further comprise determining a plurality of voltage null counts and a plurality of current null counts when no power is applied to the heater, and wherein the resistance value is further based on the plurality of voltage null counts and the plurality of current null counts.

19. each of the plurality of voltage null counts is associated with one of the plurality of dynamic gain levels; 20. The system of claim 18, wherein each of the plurality of current null counts is associated with one of the plurality of dynamic gain levels.

20. The instructions further include: determining a voltage value based on a difference between the voltage count and a predetermined voltage null count of the plurality of voltage null counts; determining a current value based on a difference between the current count and a predetermined current null count of the plurality of current null counts; further comprising 20. The system of claim 18, wherein the resistance value of the resistive heating element is further based on the voltage value and the current value.

21. 13. The system of claim 12, wherein the instructions further comprise determining a plurality of voltage drift counts and a plurality of current drift counts, and wherein the resistance value is further based on the plurality of voltage drift counts and the plurality of current drift counts.

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