Heater control system based on supply current slope

Abstract

The heater control system includes a heater driver, a current sensor, a slope calculator, and a mode selector. The heater driver is configured to control current to the heater. The current sensor is configured to sense the current provided to the heater. The slope calculator is configured to calculate a slope of the current provided to the heater. The mode selector is configured to adjust the current provided to the heater by the heater driver based on the slope of the current.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to U.S. Patent Application No. 16 / 793,436, filed February 18, 2020. The entire disclosure of that application is incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to heater control systems, and in particular to heater control systems without temperature sensors. BACKGROUND

[0004] The background description provided herein is for the purpose of generally presenting the context of the disclosure. The work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that can not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the application.

[0005] When a passenger enters a vehicle after a long period of time with the vehicle turned off in a cold ambient environment, the temperature of the exposed interior surfaces of the vehicle is at, or near, the ambient temperature. The interior surfaces can initially be uncomfortable to feel when a passenger enters the vehicle after a long period of time immersed in a low ambient temperature. Heaters are used to heat some of the exposed interior surfaces of the vehicle that come into contact with the vehicle occupants. For example, heaters can be used to heat the seats and / or steering wheel of the vehicle. When turned on, the heaters quickly heat the exposed interior surfaces to a comfortable temperature without overheating the surfaces.

[0006] Control systems for heaters used in seats and steering wheels can include one or more temperature sensors to sense the temperature of the exposed surfaces. The temperature sensors can include negative temperature coefficient (NTC) temperature sensors. Each temperature sensor tracks the local temperature of a portion of the seat or steering wheel. A controller receives the sensed temperature of the temperature sensors, estimates the temperature of the corresponding surface, and adjusts the power output to the corresponding heater.

[0007] Some manufacturers use heater control systems that do not use temperature sensors. For example, these heater control systems can determine the temperature of the exposed interior surfaces by calculating the resistance of the heating wire during heating based on the instantaneous resistance, the thermal coefficient of the heating wire, and a reference resistance of the heater at a known temperature (e.g., during manufacturing or at vehicle start-up with a temperature sensor). However, some manufacturers can refuse to provide the known temperature reference.

[0008] Some heater control systems attempt to determine the heating wire temperature based on the current provided to the heater. This method can be used if the resistance of the heating wire can be accurately determined. However, this method does not work in systems that have a relatively high resistance tolerance range (e.g. + / - 10%). In systems that have a relatively high resistance tolerance range, a reference resistance can be used to increase accuracy. However, using a reference resistance is relatively complex and expensive. SUMMARY

[0009] A heater control system is provided that includes a heater driver, a current sensor, a slope calculator, and a mode selector. The heater driver is configured to control the current provided to the heater. The current sensor is configured to sense the current provided to the heater. The slope calculator is configured to calculate the slope of the current provided to the heater. The mode selector is configured to adjust the current provided to the heater by the heater driver based on the slope of the current.

[0010] In other features, the heater driver is configured to use pulse width modulation (PWM) with a duty cycle, and wherein the mode selector is configured to adjust the duty cycle of the heater based on the slope of the current.

[0011] In other features, the mode selector is configured to define a range of slopes, select one of the range of slopes based on the slope of the current, and adjust the current provided by the heater based on the selected one of the range of slopes.

[0012] In other features, the heater control system further includes a low pass filter disposed between the current sensor and the slope calculator.

[0013] In other features, the mode selector is configured to receive a battery voltage value and adjust the current provided to the heater based on the battery voltage value.

[0014] In other features, the mode selector includes N modes, where N is an integer greater than 2, and wherein each of the N modes corresponds to a different range of current slopes.

[0015] In other features, the mode selector is configured to decrease the duty cycle of the heater driver as the slope of the current decreases.

[0016] In other features, the heater control system further includes a timer configured to reset when the heater is turned on, wherein the mode selector is configured to select a predetermined duty cycle for the heater after the timer reaches a predetermined time period.

[0017] In other features, the mode selector includes a first mode, a second mode, and a third mode. The first mode is selected when the slope of the current is within a first current slope range. The first duty cycle is selected by the mode selector when the slope of the current is within the first current slope range. The second mode is selected when the slope of the current is within a second current slope range. The second duty cycle is selected by the mode selector when the slope of the current is within the second current slope range. The third mode is selected when the slope of the current is within a third current slope range. The third duty cycle is selected by the mode selector when the slope of the current is within the third current slope range. The first current slope range is greater than the second current slope range. The second current slope range is greater than the third current slope range. The first duty cycle is greater than the second duty cycle. The second duty cycle is greater than the third duty cycle.

[0018] In other features, a system is provided that includes a heater control system, a heater, and a seat that includes the heater.

[0019] In other features, a system is provided that includes a heater control system, a heater, and a steering wheel that includes the heater.

[0020] In other features, a heater control system is provided that includes a heater driver, a current sensor, a slope calculator, and a temperature estimator. The heater driver is configured to provide a current to a heater. The current sensor is configured to sense the current provided to the heater. The slope calculator is configured to calculate a slope of the current provided to the heater. The temperature estimator is configured to estimate a temperature of a heating surface based on the slope of the current. The heater driver is configured to receive a temperature setpoint and the estimated temperature of the heating surface.

[0021] In other features, the heater driver is configured to use pulse width modulation (PWM) with a duty cycle, and wherein the heater driver is configured to adjust the duty cycle of the heater based on a difference between the temperature setpoint and the estimated temperature of the heating surface.

[0022] In other features, the heater control system further includes a low pass filter disposed between the current sensor and the slope calculator.

[0023] In other features, the heater driver is configured to receive a battery voltage value and further adjust the current provided to the heater based on the battery voltage value.

[0024] In other features, the heater driver is configured to decrease a duty cycle of the heater driver as the slope of the current decreases.

[0025] In other features, a system is provided that includes a heater control system, a heater, and a seat that includes the heater.

[0026] In other features, a system is provided that includes a heater control system, a heater, and a steering wheel that includes the heater.

[0027] Other applications of the disclosure will become apparent to those skilled in the art from consideration of the detailed description and accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0028] The present disclosure will become more fully understood from the detailed description and accompanying drawings, wherein:

[0029] Figure 1 is a functional block diagram of an example of a heater control system according to the present invention;

[0030] Figure 2A and FIG. 2B are functional block diagrams of other examples of a heater control system according to the present disclosure;

[0031] Figure 3A is a graph showing current provided to a heater and temperature of a heating wire according to the present invention;

[0032] Figure 3B is a graph showing current provided to a heater, temperature of a heating wire, and different current slope regions according to the present invention;

[0033] Figure 4 is a flowchart of a method of controlling a heater based on a current slope according to the present invention; and

[0034] Figure 5 is a flowchart of a method of controlling a heater based on a current slope according to the present invention.

[0035] In the drawings, reference numerals can be repeated among the figures for like and / or similar elements. DETAILED DESCRIPTION

[0036] While the foregoing disclosure relates to seat heaters and / or steering wheels, the systems and methods described herein can be used for other heaters in other locations. The present disclosure relates to a heater control system that senses a slope of a current provided to the heater and estimates a temperature of a surface being heated based on the slope. In other examples, the slope of the current provided to the heater is used to determine when to switch a heater driver from a high or variable duty cycle mode to a predetermined or fixed duty cycle mode to initiate rapid heating of an internal surface to maintain a target temperature range without causing discomfort to an occupant.

[0037] The heater control system does not require a temperature sensor or reference resistor. As a result, at least two terminals of the temperature sensor, connecting wires, and heater connector can be eliminated, which reduces cost. Eliminating components such as temperature sensors and wiring also tends to increase reliability. In other words, precise control of the temperature of the seat surface can be achieved at a lower cost without a temperature sensor or reference resistor.

[0038] Due to the positive temperature coefficient (PTC) effect of the heating wire, the current supplied to the heater tends to decrease as the heating wire self-heats. As the temperature of the heating wire increases, the PTC effect causes an exponential decrease in the current that is not constant. In other words, the rate of change or slope d of the current decreases proportionally as the temperature of the wire increases. There is a fixed correlation based on the particular seat and heater design used. By monitoring the slope of the current, the wire temperature and seat surface temperature can be accurately estimated.

[0039] The current level can also depend on the voltage received from the battery. For example, after starting the vehicle after a long soak, the voltage of the battery can be low. Therefore, in some examples, different scaling factors or adjustments can be used based on where the battery voltage lies relative to a nominal battery voltage and / or a plurality of voltage ranges. The self-heating rate of the wire is primarily affected by the heat transfer to surrounding components and should not vary significantly with the resistance tolerance of the finished product.

[0040] In some examples, the slope of the current is monitored after the heater is turned on to determine when the heater is approaching the target operating temperature. When the slope indicates that the target operating temperature is reached, the controller switches to a predetermined or fixed duty cycle to maintain the required temperature. In other words, the duty cycle that accurately maintains the desired seat surface temperature is calibrated for the seat. The systems and methods described herein eliminate the temperature sensor and related components in the heater control system while maintaining precise temperature control of the heated surface.

[0041] Reference will now be made to Figure 1 The heater controller 10 includes a heater driver 20. In some examples, the heater driver 20 generates a pulse width modulation (PWM) signal with a variable duty cycle (DC) that is output to the heater 40 (e.g., for a seat, steering wheel, or other heated surface). It can be appreciated that a higher DC value can be used when the surface to be heated is cold / cold to reduce the time required to heat the surface. A lower DC value can be used as the temperature of the heating wire and internal surface increases to prevent discomfort due to overheating.

[0042] A current sensor 30 is arranged between the heater driver 20 and the heater 40 to sense the current I raw In some examples, a low pass filter 50 is used to smooth the current Iraw The filtered current I is filtered to reduce noise and generate a filtered current I filtered .

[0043] The slope calculator 54 receives the filtered current I filtered , calculates a slope of the filtered current I filtered over a predetermined time period, and outputs a current slope I slope . The temperature estimator 60 estimates a temperature of the heated surface based on the current slope I slope . By way of example only, the temperature estimator 60 includes a lookup table or a formula that determines an estimated temperature T slope based on the current slope I est .

[0044] In some examples, the temperature estimator 60 uses the current slope I slope to index a lookup table. In some examples, the temperature estimator 60 further determines the estimated temperature T est based on a voltage of the battery Vbatt. For example, the temperature estimator 60 compares the battery voltage V batt to a nominal battery voltage and / or two or more voltage ranges, and selects one of a plurality of lookup tables or formulas or adjusts the formula based on the comparison. The temperature estimator 60 then accesses the selected lookup table, uses the selected formula, or adjusts the formula based on the current slope I slope . The heater driver 20 receives the temperature setpoint T set and the estimated temperature T est , and sets a DC based thereon. In some examples, the DC is set based on a difference between the temperature setpoint T set and the estimated temperature T est .

[0045] Referring now to Figure 2A , the heater controller 100 is shown to include a heater driver 120. In some examples, the heater driver 120 generates a PWM signal having a variable duty cycle (DC) that is output to a heater 140 (e.g., for a seat, steering wheel, or other exposed interior surface of a vehicle). It can be appreciated that a higher DC value can be used when the surface to be heated is cool / cold to quickly heat the surface. A lower DC value can be used as the temperature of the heating wire and the interior surface increases.

[0046] A current sensor 130 is arranged between the heater driver 120 and the heater 140 to sense a current I raw supplied to the heater 140. In some examples, a low pass filter 150 is used to filter the current I raw to reduce noise and generate a filtered current I filtered .

[0047] The slope calculator 154 receives the filtered current I filtered , calculates the slope of the filtered current I filtered , and outputs the current slope I slope . The heating mode selector 160 selects a heating mode based on the current slope I slope . In some examples, the heating mode selector 160 compares the current slope I slope to one of a plurality of slope ranges and selects a mode for the heater based thereon. In other words, the heating mode selector 160 selects different heating control parameters based on the current slope I slope . In some examples, the heating mode selector 160 selects one of a plurality of DC values for the heater driver 120 based on the current slope I slope .

[0048] In some examples, the heating mode selector 160 includes a lookup table or a formula that outputs a desired DC based on the current slope I slope . In some examples, the heating mode selector 160 indexes a lookup table using the current slope I slope . In some examples, the heating mode selector 160 selects one of a plurality of heating modes based on the current slope I slope , which will be described further below. The heating mode selector 160 can select a lookup table or formula or adjust the formula based on the battery voltage V batt .

[0049] Referring now to Figure 2B , another heater controller 170 is shown. The heater controller 170 also includes a timer 180 that is reset when the heater transitions to an on state. In some examples, the heating mode selector 160 transitions to an open loop mode where the DC of the heater driver 120 is set to a predetermined or fixed DC after a predetermined operating period to maintain the selected heater setting determined by the timer 180.

[0050] Referring now to Figure 3A and Figure 3B , the current provided to the heater and the temperature of the heating wire are shown in the graphs. In Figure 3B , the current is sampled over time and the current slope I slope is calculated over a predetermined period. In Figure 3BWhen the heater is initially turned on after being immersed for a long time at low ambient temperatures, a steep slope value typically occurs. When the heating wire and the interior surface are cold, the current provided to the heater 140 is relatively high, and decreases rapidly due to self-heating of the heating wire. At this time, the slope of the current is in a first or high slope range. When the target slope range is reached, the heating mode selector 160 can set a relatively high DC value to quickly heat the surface without causing discomfort to the occupant.

[0051] When the wire self-heats, the current continues to decrease, and the slope of the current decreases from the high slope range to a lower slope value corresponding to a second or intermediate slope range. The heating mode selector 160 can decrease the DC value to heat the surface less quickly, thereby avoiding causing discomfort to the occupant. When the wire heats further, the current decreases further and begins to stabilize. The slope value of the current decreases to the target slope range. In some examples, a target or fixed duty cycle is used when in the target slope range.

[0052] When using the heater control system in Figure 2A , the target duty cycle is reached when the current slope I slope reaches the target slope range (independent of time). When using the heater control system in Figure 2B , the target duty cycle is reached when the current slope I slope reaches the target slope range or a predetermined period of the timer expires, whichever occurs first.

[0053] Referring now to Figure 4 , a flowchart of a method 300 for controlling a heater based on current slope is shown. At 210, the method determines whether the heater is on. If 210 is true, the method continues at 214 and optionally determines the battery voltage. At 226, the method measures the current provided to the heater. In some examples, low pass filtering is used to reduce noise in the measured current. At 230, the method determines the slope of the current. At 238, the method estimates the temperature of the heated surface based on the current and optionally the voltage of the battery. In some examples, the heater driver sets the DC based on the temperature setpoint and the estimated temperature. In other examples, at 242, the heater driver sets the DC based on the difference between the temperature setpoint and the estimated temperature.

[0054] Referring now to Figure 5 , a flowchart of a method 300 for controlling a heater based on current slope is shown. At 310, the method determines whether the heater is on. If 310 is true, the method continues at 314 and optionally determines the battery voltage. At 318, the method optionally selects a voltage range corresponding to the battery voltage. At 322, the method optionally selects or adjusts a current slope lookup table or formula based on the selected voltage range of the battery voltage.

[0055] At 326, the method measures the current provided to the heater. In some examples, low pass filtering is used to reduce noise. At 330, the method determines the slope of the current. At 340, the method determines whether the current slope is within a first slope range. If 340 is true, then at 344 the heater is operated using a first set of heater parameters. For example, the first set of heater parameters can set the DC of the heater driver to a first value or a first range of DC values.

[0056] If 340 is false, then at 350 the method determines whether the current slope is within a second slope range. If 340 is true, then at 354 the heater is operated using a second set of heater parameters. For example, the second set of heater parameters can set the DC of the heater driver to a second value or a second range of DC values. In some examples, the second value or DC range is less than the first value or DC range.

[0057] If 350 is false, then at 360 the heater is operated using a third set of heater parameters. For example, the third set of heater parameters can set the DC of the heater driver to a fixed DC value or a third range of DC values. In some examples, the third value or DC range is less than the first value or DC range and the second value or DC range. While three different modes are shown, more or fewer modes can be used.

[0058] The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be limited to such examples. The methods of the disclosure will be apparent to those skilled in the art, including, one or more steps within the methods can be performed in different orders (or simultaneously) and without departing from the principles of the present disclosure. Further, although each of the embodiments describes certain features, any one or more of those features described in relation to any of the embodiments of the disclosure can be implemented and / or combined in the features of any other embodiment, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and substitution of one or more embodiments for one another is within the scope of the disclosure.

[0059] Various terminologies are used to describe spatial and functional relationships among elements (e.g., between a module, circuit elements, semiconductor layers, etc.), including "connected", "engaged", "coupled", "adjacent", "immediately adjacent", "on", "above", "under", and "disposed". Unless explicitly described as "direct", when a relationship between first and second elements is described in the above disclosure, the relationship can be a direct relationship in which no other intervening element is between the first and second elements, but can also be an indirect relationship in which one or more intervening elements (spatially or functionally) are between the first and second elements. As used herein, the phrase "at least one of A, B, and C" should be interpreted as meaning using non-exclusive logic OR of 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".

[0060] In the drawings, the direction of an arrow, as indicated by the arrowhead, is generally indicative of information flow (e.g., data or instructions) unless otherwise noted. For instance, when element A and element B exchange a variety of information but the information sent from element A to element B is relevant to a discussion of the illustration, a drawing can indicate an arrow pointing from element A to element B. This unidirectional arrow does not imply that no other information is sent from element B to element A. In addition, for information sent from element A to element B, element B can send a request for the information to element A, or receive the information in response to a request from element B.

[0061] In this application, including the definitions below, the term "module" or the term "controller" can be replaced with the term "circuit." The term "module" can refer to, be part of, or include: an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combination of combination of

[0062] The module can include one or more interface circuits. In some examples, the interface circuits can include wired or wireless interfaces that are connected to a local area network (LAN), the Internet, a wide area network (WAN), or combinations thereof. The functionality of any given module of the present disclosure can be distributed among multiple modules that are connected via interface circuits. For example, a plurality of modules can allow load balancing. In another example, a server (also known as remote, or cloud) module can implement certain functionality on behalf of a client module.

[0063] As described above, the term code can include software, firmware, and / or microcode, and can refer to program, routines, functions, classes, data structures, and / or objects. The term shared processor circuitry includes a single processor circuitry executing some or all code from multiple modules. The term group processor circuitry includes a processor circuitry, with the additional processor circuitry, executing some or all code from one or more modules. A reference to multiple processor circuitries includes multiple processor circuitries on discrete dies, multiple processor circuitries on a single die, multiple cores of a single processor circuitry, multiple threads of a single processor circuitry, or a combination of the above. The term shared memory circuitry includes a single memory circuitry storing some or all code from multiple modules. The term group memory circuitry includes a memory circuitry, with the additional memory, storing some or all code from one or more modules.

[0064] The term storage circuitry is a subset of the term computer-readable medium. The term computer-readable medium, as used herein, does not encompass transitory propagating signals per se (e.g., a changing electric or electromagnetic field that propagates between two physical locations). The term computer-readable medium thus can be considered tangible and non-transitory. Non-limiting examples of non-transitory, tangible computer-readable media are nonvolatile memory circuits (e.g., flash memory circuits, erasable programmable read-only memory circuits, or mask read-only memory circuits), volatile memory circuits (e.g., static or dynamic random- access memory circuits), magnetic storage media (e.g., magnetic tapes or magnetic hard drives), and optical storage media (e.g., optical discs).

[0065] The apparatus and methods described in this application can be partially or entirely implemented by a special purpose computer created by configuring a general purpose computer to execute one or more particular functions embodied in computer programs.

[0066] A computer program includes processor-executable instructions stored on at least one non-transitory, tangible computer-readable medium. A computer program can also include or rely on stored data. A computer program can encompass a Basic Input-Output system (BIOS) that interacts with hardware of the special purpose computer, device drivers that interact with particular devices of the special purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0067] The computer programs can include: (i) descriptive text to be parsed, such as HTML (HyperText Markup Language), XML (Extensible Markup Language), or JSON (javascript Object Notation) (ii) assembly code, (iii) object code that has been generated by a compiler from source code, (iv) source code that is executed by an interpreter, (v) source code that is both compiled and executed by a just-in-time compiler, etc. The source code can be written using a programming language, such as, for example only, C, C++, C#, objectyc, Swift, Haskell, Go, SQL, R, Lisp, Fortran, Perl, Pascal, Curl, OCaml, HTML5 (HyperText Markup Language Fifth Revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Visual Basic, Lua, MATLAB, SIMULINK, and Java, and / or Python. The computer programs can include machine code that has been generated by a compiler from a source code, or machine code that is executed by an interpreter, or machine code that is both compiled and executed by a just-in-time compiler, etc. The computer programs can include machine code that has been generated by a compiler from a source code, or machine code that is executed by an interpreter, or machine code that is both compiled and executed by a just-in-time compiler, etc.

Claims

1. A heater control system, comprising: A heater driver is configured to control the current to the heater; A current sensor is configured to sense the current supplied to the heater; A slope calculator is configured to calculate the slope of the current supplied to the heater; as well as A mode selector is configured to define multiple slope ranges, select one of the multiple slope ranges based on the slope of the current, and adjust the current supplied to the heater by the heated driver based on the selected slope range.

2. The heater control system of claim 1, wherein the heater driver is configured to use pulse width modulation (PWM) with a duty cycle, and wherein the mode selector is configured to adjust the duty cycle of the heater based on the slope of the current.

3. The heater control system of claim 1, further comprising a low-pass filter disposed between the current sensor and the slope calculator.

4. The heater control system of claim 1, wherein the mode selector is configured to receive a battery voltage value and adjust the current supplied to the heater based on the battery voltage value.

5. The heater control system according to claim 1, wherein the mode selector comprises N modes, where N is an integer greater than 2, and wherein each of the N modes corresponds to a different current slope range.

6. The heater control system of claim 1, wherein the mode selector is configured to decrease the duty cycle of the heater driver as the slope of the current decreases.

7. The heater control system of claim 1, further comprising a timer configured to reset when the heater is turned on, wherein the mode selector is configured to select a predetermined duty cycle for the heater after the timer reaches a predetermined time period.

8. The heater control system according to claim 1, wherein: The mode selector includes a first mode, a second mode, and a third mode; The first mode is selected when the slope of the current is within the range of the first current slope. When the slope of the current is within the range of the first current slope, the mode selector selects the first duty cycle; The second mode is selected when the slope of the current is within the range of the second current slope; When the slope of the current is within the range of the second current slope, the mode selector selects the second duty cycle; The third mode is selected when the slope of the current is within the range of the third current slope; When the slope of the current is within the range of the third current slope, the mode selector selects the third duty cycle; The first current slope range is greater than the second current slope range; The second current slope range is greater than the third current slope range; The first duty cycle is greater than the second duty cycle; as well as The second duty cycle is greater than the third duty cycle.

9. A system comprising: The heater control system according to claim 1; The heater; as well as Seat, including the heater.

10. A system comprising: The heater control system according to claim 1; The heater; as well as Steering wheel, including the heater.

11. A heater control system, comprising: A heater driver is configured to supply current to the heater; A current sensor is configured to sense the current supplied to the heater; A slope calculator is configured to calculate the slope of the current supplied to the heater; as well as A temperature estimator is configured to estimate the temperature of the heated surface based on the slope of the current. The heater driver is configured to receive a temperature setpoint and an estimated temperature of the heated surface using pulse width modulation (PWM) with a duty cycle, and the heater driver is configured to adjust the duty cycle of the heater based on the difference between the temperature setpoint and the estimated temperature of the heated surface.

12. The heater control system of claim 11, further comprising a low-pass filter disposed between the current sensor and the slope calculator.

13. The heater control system of claim 11, wherein the heater driver is configured to receive a battery voltage value and further adjust the current supplied to the heater based on the battery voltage value.

14. The heater control system of claim 11, wherein the heater driver is configured to decrease the duty cycle of the heater driver as the slope of the current decreases.

15. A system comprising: The heater control system according to claim 11; The heater; as well as Seat, including the heater.

16. A system comprising: The heater control system according to claim 11; The heater; as well as Steering wheel, including the heater.

Images