Description:FIELD OF THE INVENTION

The present invention generally relates to Contact Position Input Sense Via Floating Output Voltage. More specifically, the use of an operational amplifier (OP-AMP) and a MCU (microcontroller unit) to automate the working of the air conditioning unit.

BACKGROUND OF THE INVENTION

An air conditioning unit in an automobile is employed to provide cooling to occupants of the vehicle. The air conditioning unit may include an air-cooling system that cools the air and a blower that is adapted to blow the air through the air-cooling system to cool the air. The air conditioning unit may also include a set of knobs that can control the fan blower speed and amount of cooling achieved.

The air conditioning unit is configured in such a way that the air-cooling system does not get activated when the blower knob is set at the OFF condition. The air conditioning unit generally uses an operational amplifier (OP-AMP) that generates a signal corresponding to the OFF condition of the fan knob for a controller. The OP-AMP is configured to compare two voltage signals associated with the fan blower. The OP-AMP works on the principle that an inverting voltage input signal is less than a non-inverting voltage input signal when the blower knob is at OFF state. Further, when the blower knob is operated, the non-inverting voltage input signal drops below the inverting voltage input which causes the OP-AMP not to generate the digital signal which prompts the controller to switch ON the air-cooling system.

There are some limitations of the current technique of detecting the OFF state of the blower knob. There are cases where the performance of the vehicle battery tends to degrade, and such degradation reduces the non-inverting voltage input signal. In some cases, the non-inverting voltage input signal drops less than the inverting voltage input signal resulting in the inadvertent non-generation of a digital signal. The inadvertent non-generation of digital signals results in false activation of the air conditioning unit.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts, in a simplified format, that are further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention and nor is it intended for determining the scope of the invention.

In the proposed design OP-AMP (Operational Amplifier) which is an electronic part is used to sense the Contact voltage which is coming out from the contact of a switch for different positions of the blower speed knob, Vo voltage is controlled by the resistance combinations to tune for the sensing for a particular position of the knob. Further, a Resistance based voltage divider circuit is used that may be configured to lower the inverting voltage input signal by a pre-set ratio so that the inverting voltage input signal is less than the non-inverting voltage input signal.

In an embodiment, an air conditioning (AC) control circuit is disclosed that includes a voltage source having a positive terminal and a ground terminal; a blower fan circuit, and a switch circuit operably coupled to the voltage source and the blower circuit. The blower fan circuit includes a blower motor having a positive terminal coupled to the ground terminal of the voltage source. In addition, the blower fan circuit includes a resistor unit having a first terminal coupled to a negative terminal of the blower motor, such that the resistor unit comprising a plurality of resistors adapted to provide a range of electrical resistances to the blower motor. The blower fan circuit also includes a knob having a first terminal coupled to the ground terminal of the voltage source and adapted to selectively connect to a terminal of each of the plurality of the resistor to introduce an electrical resistance from the range of electrical resistances to the blower motor regulate a speed of blower motor. The switch circuit includes an operational amplifier (OP-AMP) that further includes a non-inverting terminal coupled to the negative terminal of the blower motor, an inverting terminal, a source terminal coupled to the positive terminal of the voltage source, a sink terminal coupled to the ground terminal of the voltage source, and an output terminal adapted to output a signal based on a comparison between voltages at the non-inverting terminal and the inverting terminal. Further, the AC control circuit includes a voltage regulator having a first terminal coupled to the positive terminal of the voltage source and a second terminal coupled to the inverting terminal, such that the voltage regulator is adapted to reduce the voltage at the inverting terminal from the non- inverting terminal by a predefined ratio.

According to the present disclosure, the resistance-based voltage divider circuit automatically lowers the inverting voltage input signal when there is a drop in the voltage from the vehicle battery. Therefore, any fluctuations in the voltage by the voltage source does not result in false activation of the air conditioner.

To further clarify advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

Figure 1 illustrates an air conditioning (AC) control circuit showing the OFF-position of a knob, according to an embodiment of the present disclosure;
Figure 2 illustrates the first position of the blower motor on the Blower fan circuit, according to an embodiment of the present disclosure;
Figure 3 illustrates the second position of the blower motor on the Blower fan circuit, according to an embodiment of the present disclosure;
Figure 4 illustrates the third position of the blower motor on the Blower fan circuit, according to an embodiment of the present disclosure; and
Figure 5 illustrates the fourth position of the blower motor on the Blower fan circuit, according to an embodiment of the present disclosure.

Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

DETAILED DESCRIPTION OF THE FIGURES

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

For example, the term “some” as used herein may be understood as “none” or “one” or “more than one” or “all.” Therefore, the terms “none,” “one,” “more than one,” “more than one, but not all” or “all” would fall under the definition of “some.” It should be appreciated by a person skilled in the art that the terminology and structure employed herein is for describing, teaching, and illuminating some embodiments and their specific features and elements and therefore, should not be construed to limit, restrict or reduce the spirit and scope of the present disclosure in any way.

For example, any terms used herein such as, “includes,” “comprises,” “has,” “consists,” and similar grammatical variants do not specify an exact limitation or restriction, and certainly do not exclude the possible addition of one or more features or elements, unless otherwise stated. Further, such terms must not be taken to exclude the possible removal of one or more of the listed features and elements, unless otherwise stated, for example, by using the limiting language including, but not limited to, “must comprise” or “needs to include.”

Whether or not a certain feature or element was limited to being used only once, it may still be referred to as “one or more features” or “one or more elements” or “at least one feature” or “at least one element.” Furthermore, the use of the terms “one or more” or “at least one” feature or element do not preclude there being none of that feature or element, unless otherwise specified by limiting language including, but not limited to, “there needs to be one or more…” or “one or more elements is required.”

Unless otherwise defined, all terms and especially any technical and/or scientific terms, used herein may be taken to have the same meaning as commonly understood by a person ordinarily skilled in the art.

Reference is made herein to some “embodiments.” It should be understood that an embodiment is an example of a possible implementation of any features and/or elements of the present disclosure. Some embodiments have been described for the purpose of explaining one or more of the potential ways in which the specific features and/or elements of the proposed disclosure fulfil the requirements of uniqueness, utility, and non-obviousness.

Use of the phrases and/or terms including, but not limited to, “a first embodiment,” “a further embodiment,” “an alternate embodiment,” “one embodiment,” “an embodiment,” “multiple embodiments,” “some embodiments,” “other embodiments,” “further embodiment”, “furthermore embodiment”, “additional embodiment” or other variants thereof do not necessarily refer to the same embodiments. Unless otherwise specified, one or more particular features and/or elements described in connection with one or more embodiments may be found in one embodiment, or may be found in more than one embodiment, or may be found in all embodiments, or may be found in no embodiments. Although one or more features and/or elements may be described herein in the context of only a single embodiment, or in the context of more than one embodiment, or in the context of all embodiments, the features and/or elements may instead be provided separately or in any appropriate combination or not at all. Conversely, any features and/or elements described in the context of separate embodiments may alternatively be realized as existing together in the context of a single embodiment.

Any particular and all details set forth herein are used in the context of some embodiments and therefore should not necessarily be taken as limiting factors to the proposed disclosure.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

For the sake of clarity, the first digit of a reference numeral of each component of the present disclosure is indicative of the Figure number, in which the corresponding component is shown. For example, reference numerals starting with digit “1” are shown at least in Figure 1. Similarly, reference numerals starting with digit “2” are shown at least in Figure 2.

Figure 1 illustrates an air conditioning (AC) control circuit 100 for controlling operation of a heat ventilation and air conditioning (HVAC) unit, showing a knob 114 at OFF-position, according to an embodiment of the present disclosure. The AC control circuit 100 represents a circuit diagram constructed for the working of the air conditioning system of an automobile. In one example, the control circuit 100 may operate a compressor of the HVAC unit. The AC control circuit 100 includes but is not limited to a voltage source 102 may include a ground terminal and a positive terminal, a blower fan circuit 104, and a switch circuit 106. Further, the blower fan circuit 104 and the switch circuit 106 are connected to the voltage source 102.

In one example, the blower fan circuit 104 may include components, such as, but is not limited to a blower motor 108, such that a positive terminal of the blower motor 108 is connected to the positive terminal of the voltage source 102. The blower motor 108 may be coupled to a blower fan (not shown) and may be adapted to change the speed of air flow flowing through vents of the HVAC unit. The blower fan circuit 104 may also include a resistor unit 110 that is operably coupled to the blower motor 108 and may include a plurality of resistors 126, 128, and 130. The resistor unit 110 is adapted to change a speed of the blower fan by changing the voltage going to the blower motor 108. Accordingly, the resistor unit 110 may offer different value of resistance to the current flowing into the blower motor 108. The resistor unit 110 may have a first terminal connected to the negative terminal of the blower motor 108.

In one example, the resistor 130 may have a first terminal and a second terminal connected in series to the negative terminal to the blower motor 108. Further, resistor 128 may have a first terminal connected in series to a first terminal of the resistor 130. Furthermore, the resistor 126 may have a first terminal connected in series to a terminal of the resistor 128.

In addition, the blower fan circuit 104 may include the knob 114 that may interact with the resistor unit 110. The knob 114 may include a first terminal connected to the ground terminal and a second terminal. The second terminal of the knob 114 can selectively connect to a terminal of each of the plurality of the resistors 126, 128, 130 in order to regulate the speed of the blower motor 108 by regulating the resistance of the blower fan circuit 104, and a plurality of resistors. The blower motor 108 can be operated in various modes by the knob 114 so as to provide air conditioning in the automobile at the user’s convenience.

The knob 114 is adapted to toggle between the plurality of regulator positions either linearly or rotationally and hence selectively connecting to the plurality of resistors 126, 128, and 130 in a predetermined sequence. In one example, each of the resistor 130, 128, and 126 has a second terminal, and the knob 114 is adapted to connect to a second terminal of one of the resistors 130, 128, and 126 to change the value of electrical resistance. While the first end of the knob 114 moves to switch between the plurality of regulator positions, the other end is either connected back to the ground terminal of the voltage source 102 hence completing the circuit. In one example, the plurality of regulator positions in the blower fan circuit 104 include but are not limited to an off-position 116 in which the knob 114 is disconnected from the resistor unit 110 as shown in Figure 1.

During the operation, the knob 114 can translate from the aforementioned position, such that the knob 114 may connect with each of the aforementioned resistors to vary the total resistance to the current flowing through the blower motor 108. In one example, at the OFF position, the knob 114 is not connected to the resistor 126 as shown in Figure 1 thereby maintaining an open circuit that keeps the blower motor 108 OFF.

In one example, the switch circuit 106 is a circuit assembly designed to regulate and determine the switch-off and switch-on conditions of the air conditioner based on the output produced by the operational amplifier (OP-AMP) 136. The switch circuit 106 may include includes but is not limited to an operational amplifier (OP-AMP) 136 circuit, and an MCU 138. Details of the OP-AMP 136 is explained from the next paragraph.

The OP-AMP 136 is an operational amplifier working as a comparator. The OP-AMP 136 may include a non-inverting terminal 172 coupled to the negative terminal of the blower motor 108 and an inverting terminal 160. The OP-AMP 136 may also include a source terminal 154 coupled to the ground terminal of the voltage source 102 and a sink terminal coupled to the positive terminal of the voltage source 102. Finally, the OP-AMP 136 may include an output terminal 146 adapted to output a signal based on a comparison between voltages at the non-inverting terminal 172 and the inverting terminal 160.

In addition, the AC control circuit 100 may include various components that connects the aforementioned terminals to other components of the voltage source 102 and the blower fan circuit 104. For instance, the AC control circuit 100 may include a resistor 150 having a terminal connected to positive terminal to the voltage source 102 and a resistor 156 connected in parallel to another terminal of the resistor 150 and to the ground terminal. In addition, the AC control circuit 100 may include a resistor 158 having a terminal connected in parallel to resistor 150 and resistor 156 and another terminal connected in series to the inverting terminal 160. Further, the AC control circuit 100 may include a resistor 170 having a terminal connected the non-inverting terminal 172 and a diode 162 having an cathode terminal connected to the negative terminal of the blower fan. Further, the AC control circuit 100 may include a resistor 148 having a terminal connected to the positive terminal of the voltage source 102 and another terminal connected in parallel to the terminal of the resistor 170 and a diode 152 is parallelly connected to the resistor 148 and an anode terminal connected to the terminal of resistor 170.

In one example, the switch circuit 106 may include a capacitor 164 coupled to a cathode terminal of the diode 162 and the ground terminal of the voltage terminal and a Schottky diode 166 coupled to the anode terminal of the diode 162 and cathode of Schottky diode 166 is connected to the ground terminal of the voltage source 102.

As shown in Figure 1, the switch circuit 106 may also include a controller 138 having a digital input pin D0 connected to the output terminal 146 and adapted to receive the output signal. Further, the controller 138 is adapted to deactivate a compressor of the HVAC unit based on the receipt of the output signal. The switch circuit 106 may also include a Zener diode 174 that has a cathode terminal connected to the output terminal 146 and the digital input pin D0 and anode terminal of Zener diode 174 is connected with ground terminal. In addition, the switch circuit 106 may include a capacitor 176 that has a terminal connected to the output terminal 146 and the digital input pin D0, and another terminal connected to the ground terminal.

According to the present disclosure, the OP-AMP 136 is configured to compare the voltages at the non-inverting terminal 172 and the inverting terminal 160 to generate the output signal. Further, the output signal is generated when the voltage at the non-inverting terminal 172 is greater than the voltage at the inverting terminal 160. A scenario where the voltage at the non-inverting terminal 172 is greater than the voltage at the inverting terminal 160 is when the blower motor 108 is in the open circuit or in other words, the knob 114 is at the OFF position. In this position, the contact voltage 132 is nearly equal to the voltage of the voltage source 102, which is greater value than the voltage at the inverting terminal 160, and therefore, the OP-AMP 136 may generate the output signal. At this position, the AC control unit 100 should keep the compressor of the HVAC unit deactivated because the blower motor 108 is not operating the blower fan to circulate the air.

There may be cases where the rated voltage of the voltage source 102 varies or fluctuate because of the battery degradation. The battery degradation may cause the non-inverting voltage 172 to drop. Voltage source 102 is connected to one terminal of resistor 150 the voltage regulator 112 is a voltage divider network circuit so voltage of inverting terminal also drops in ratio. Ratio is decided by the resistor 150 and 156. So as battery voltage degradation of inverting terminal voltage 160 and non-inverting terminal voltage 172 happens the comparator output remains the same as defined by the position of knob 114.

The voltage regulator 112 may have a first terminal coupled to the positive terminal of the voltage source 102 and a second terminal coupled to the inverting terminal 160, such that the voltage regulator 112 is adapted to reduce the voltage at the inverting terminal 160 from the non- inverting terminal 172 by a predefined ratio. The voltage regulator 112 may include a resistor 150 having a terminal connected to positive terminal to the voltage source 102 and a resistor 156 connected in parallel to another terminal of the resistor 150 and to the ground terminal.

According to the present disclosure, the plurality of resistors are all known as tuning resistors.

The working procedure pertaining to figure 1 has been discussed below with reference to the above-mentioned components of the AC control circuit 100. The process begins with the provided voltage source 102 which travels in 2 directions, namely one towards the blower motor 108 and the second towards the OP-AMP 136. Once the voltage source 102 reaches the OP-AMP 136, it is distributed in 2 sections, one part is used to power the OP-AMP 136 while the rest of the voltage travels to non-inverting terminal 172 and inverting terminal 160. The current travels through resistance 150 and 156 as resistance-based voltage divider circuits drop the voltage by a predetermined ratio thereby maintaining a voltage at the inverting terminal 160 terminal voltage via resistor 158 than the voltage at the non-inverting terminal 172. During the off-position 116, the only resistance produced from the blower fan circuit 104 is the blower resistance. This determines that the contact voltage 132 will be the highest value and greater than the value received at non-inverting terminal 160, hence producing the high output signal from the OP-AMP 136. The high output signal is gives to the MCU 138 which, considering the output commands the air conditioner to remain switched off.

In an example, table 1 provides an overview of practical observations made after the testing of the present disclosure. This voltage table is for concept understanding point of view. Practical value may differ but OP-AMP 136 output will be same.

Operation Contact Voltage Inverting terminal voltage OP-AMP output Status of Op-AMP terminal voltages
0 Position (Off) 12.49V 11.46V 1 (high Output) V+ > V-
1st Position 6.66V 11.46V 0 (Low Output) V+ < V-
2nd Position 4.97V 11.46V 0 (Low Output) V+ < V-
3rd Position 4.12V 11.46V 0 (Low Output) V+ < V-
4th Position 0.113V 11.46V 0 (Low Output) V+ < V-
TABLE 1

In an embodiment, whenever the battery voltage drops, which is possible due to various factors, the reduction in the voltage is auto-calibrated. The calibration has been performed in a manner such that the inverting terminal 160 has voltage lesser than the value of the non-inverting terminal 172 voltage, wherein the knob 114 is not engaged (at blower motor off, zero position) .After the regulator has been engaged, the voltage drops, but as has been previously stated, due to the auto-calibration, the voltage is dropped in a manner to maintain the balance and the working of the OP-AMP 136.

In an example, a feedback system has been created which works to give the information to the MCU 138 regarding the positioning of the knob 114. The system intercepts the changing position of the knob 114. Simultaneously, the OP-AMP 136 outputs a low or high voltage output signal for all positions, this reflects an issue within the system either at the blower fan circuit 104 or at the switch circuit 106. Under such circumstances, the feedback system executes an error code.

As mentioned before, the knob 114 may travel via different positions as explained with respect to Figures 2, 3, 4, and 5.

Figure 2 illustrates the first position of the knob 114 on the blower fan circuit 104, according to an embodiment of the present disclosure. the working procedure pertaining to figure 2 with reference to figure 1 has been discussed below. The process begins with the provided voltage source 102 which travels in 2 directions, namely one towards the blower motor 108 and the second towards the OP-AMP 136. Once the voltage source 102 reaches the OP-AMP 136, it is distributed in 2 sections, one part is used to power the OP-AMP 136 while the rest of the voltage travels to non-inverting terminal 172 and inverting terminal 160. The voltage travels through resistor 150 and 156 as resistance based voltage divider circuits 112 drop the voltage by a predetermined ratio thereby maintaining a low value at inverting terminal 160 via 158. During the first position 118, the resistance produced from the blower fan circuit 104 is the blower resistance, the resistance 126, the resistance 128, and the resistance 130. According to the Law of combination of series resistance, when resistance is connected serially, the total resistance is equal to the sum of the individual resistance produced by each resistor.

Inferring to the Law of combination of series resistance, the total resistance is:
Total Resistance = Resistance 126 + Resistance 128 + Resistance 130 + Blower resistance

This determines that the contact voltage 132 will be a value lower than the value received at off position 116 and at inverting terminal 160, hence producing the low output signal from the OP-AMP 136. The low output signal is given to the MCU 138 which, considering the output commands the air conditioner to switch on.

Figure 3 illustrates the second position of the knob 114 on the blower fan circuit 104, according to an embodiment of the present disclosure. The working procedure pertaining to figure 3 with reference to figure 1 has been discussed below. The process begins with the provided voltage source 102 which travels in 2 directions, namely one towards the blower motor 108 and the second towards the OP-AMP 136. Once the voltage source 102 reaches the OP-AMP 136, it is distributed in 2 sections, one part is used to power the OP-AMP 136 while the rest of the voltage travels to non-inverting terminal 172 and inverting terminal 160. The voltage travels through resistance 150 and 156 as resistance based voltage divider 112 circuit drop the voltage by a predetermined ratio thereby maintaining a low inverting terminal 160 via 158. During the second position 120, the resistance produced from the blower fan circuit 104 is the blower resistance, the resistance 128, and the resistance 130.

Inferring to the Law of combination of series resistance, the total resistance is:
Total Resistance = Resistance 128 + Resistance 130 + Blower resistance

This determines that the contact voltage 132 will be a value lower than the value received at off position 116, first position 118, and inverting terminal 160, hence producing the low output signal from the OP-AMP 136. The low output signal is given to the MCU 138 which, considering the output commands the air conditioner to switch on.

Figure 4 illustrates the third position of the knob 114 on the blower fan circuit 104, according to an embodiment of the present disclosure. The working procedure pertaining to figure 4 with reference to figure 1 has been discussed below. The process begins with the provided voltage source 102 which travels in 2 directions, namely one towards the blower motor 108 and the second towards the OP-AMP 136. Once the voltage source 102 reaches the OP-AMP 136, it is distributed in 2 sections, one part is used to power the OP-AMP 136 while the rest of the voltage travels to non-inverting terminal 172 and inverting terminal 160. The voltage travels through resistance 150 and 156 as resistance-based voltage divider 112 circuit drop the voltage by a predetermined ratio thereby maintaining a low inverting terminal 160 via 158. During the third position 122, the resistance produced from the blower fan circuit 104 is the blower resistance, and the resistance 130.

Inferring to the Law of combination of series resistance, the total resistance is:
Total Resistance = Resistance 130 + Blower resistance

This determines that the contact voltage 132 will be a value lower than the value received at off position 116, first position 118, second position 120, and at inverting terminal 160, hence producing the low output signal from the OP-AMP 136. The low output signal is given to the MCU 138 which, considering the output commands the air conditioner to switch on.

Figure 5 illustrates the fourth position of the knob 114 on the blower fan circuit 104, according to an embodiment of the present disclosure. The working procedure pertaining to figure 5 with reference to figure 1 has been discussed below. The process begins with the provided voltage source 102 which travels in 2 directions, namely one towards the blower motor 108 and the second towards the OP-AMP 136. Once the voltage source 102 reaches the OP-AMP 136, it is distributed in 2 sections, one part is used to power the OP-AMP 136 while the rest of the voltage travels to non-inverting terminal 172 and inverting terminal 160. The voltage travels through resistance 150 and 156 as resistance-based voltage divider 112 circuit drop the voltage by a predetermined ratio thereby maintaining a low inverting terminal 160 via 158. During the fourth position 124, the resistance produced from the blower fan circuit 104 is only the blower resistance. This determines that the contact voltage 132 will be the lowest value received, hence producing the low output signal from the OP-AMP 136. The low output signal gives to the MCU 138 which, considering the output commands the air conditioner to switch on.

Accordingly, the knob 114 is adapted to assume a zero position (shown in Figure 1), such that the knob 114 is disconnected from the resistor unit 110 and the non-inverting voltage 172 is greater than inverting voltage 160. Further, the knob 114 is adapted to assume a first position (shown in Figure 2), such that the knob 114 is connected to the terminal of the resistor 126 and value of a value of electrical resistance is submission of resistance values of Blower resistance, resistors 126, 128, and 130. In this position, the non-inverting terminal voltage 172 is lower than inverting terminal voltage 160.

The knob 114 may also assume a second position (shown in Figure 3), such that the knob 114 is connected to the terminal of the resistor 128 and value of a value of electrical resistance is submission of resistance values of Blower resistance, resistors 128 and 130. In this position, the non-inverting voltage is lower than inverting voltage;

Further, the knob 114 may assume a third position (shown in Figure 4), such that the knob 114 is connected to the terminal of the resistor 130 and value of electrical resistance is equal to a resistance value of Blower resistance, resistor 130. In this position too, the non-inverting voltage is lower than inverting voltage; and

Finally, the knob 114 may assume a fourth position (shown in Figure 5), such that the knob 114 is connected to the negative terminal of the blower motor 108. The value of electrical resistance is equal to the resistance of blower motor only. Further, the non-inverting voltage is lower than inverting voltage.

The present disclosure provides us with various advantages. For instance, the voltage regulator acts as an auto stabilization unit in spite of Changing Vehicle Operation voltage change. Further, the voltage regulator provides a simple solution to achieve stabilized output with respect to a fluctuating voltage supply. In one example, the feedback-based sensing of Blower motor fault, connection terminal break, electronics component failure. When a fault occurs in blower motor, the connection terminal breaks, and due to electronic component failure OP-AMP 136 gives always high (1) or low (0) output to the MCU 138. The MCU 138 is able to detect the fault condition because OM- AMP 136 gives same output voltage for all knob positions.

While specific language has been used to describe the present disclosure, any limitations arising on account thereto, are not intended. As would be apparent to a person in the art, various working modifications may be made to the method to implement the inventive concept as taught herein. The drawings and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment.
, Claims:1. An air conditioning (AC) control circuit (100)comprising:
a voltage source (102) having a positive terminal and a ground terminal;
a blower fan circuit (104) comprising:
a blower motor (108) having a positive terminal coupled to the positive terminal of the voltage source (102);
a resistor unit (110) having a first terminal coupled to a negative terminal of the blower motor (108), wherein the resistor unit (110) comprising a plurality of resistors (126, 128, and 130) adapted to provide a range of electrical resistances to the blower motor (108); and
a knob (114) having a first terminal coupled to the ground terminal of the voltage source (102) and adapted to selectively connect to a terminal of each of the plurality of the resistor to introduce an electrical resistance from the range of electrical resistances to the blower motor (108) regulate a speed of blower motor (108);
a switch circuit (106) operably coupled to the voltage source (102) and the blower fan circuit (104), the switch circuit (106) comprising:
an operational amplifier (OP-AMP) (136) comprising:
a non-inverting terminal (172) coupled to the negative terminal of the blower motor (108);
an inverting terminal (160);
a source terminal (154) coupled to the ground terminal of the voltage source (102);
a sink terminal coupled to the positive terminal of the voltage source (102); and
an output terminal (146) adapted to output a signal based on a comparison between voltages at the non-inverting terminal (172) and the inverting terminal (160); and
a voltage regulator having a first terminal coupled to the ground terminal of the voltage source (102) and a second terminal coupled to the inverting terminal (160), wherein the voltage regulator is adapted to reduce the voltage at the inverting terminal (160) from the non- inverting terminal (172) by a predefined ratio.

2. The AC control circuit (100) as claimed in claim 1, wherein the voltage regulator comprising:
a resistor (150) having a terminal connected to positive terminal to the voltage source (102); and
a resistor (156) connected in parallel to another terminal of the resistor (150) and to the ground terminal;

3. The AC control circuit (100) as claimed in claim 2, comprising:
A resistor (158) having a terminal connected in parallel to resistor (150) and resistor (156) and another terminal connected in series to the inverting terminal (160);
a resistor (170) having a terminal connected the non-inverting terminal (172);
a diode (162) having a cathode terminal connected to the negative terminal of the blower fan;
a resistor (148) having a terminal connected to the positive terminal of the voltage source (102) and another terminal connected in parallel to the terminal of the resistor (170); and
a diode (152) having a cathode terminal connected in parallel to the resistor (148) and an anode terminal connected to the terminal of resistor 170.

4. The AC control circuit (100) as claimed in claim 1, wherein the plurality of resistors comprises:
a resistor (130) having a first terminal and a second connected in series to the negative terminal to the blower motor (108);
a resistor (128) having a first terminal connected in series to a first terminal of the resistor (130);
a resistor (126) having a terminal connected in series to a terminal of the resistor (128);
wherein each of the resistor (130, 128, and 126) has a second terminal, and the knob (114) is adapted to connect to a second terminal of one of the resistors (130, 128, and 126) to change the value of electrical resistance.

5. The AC control circuit (100) as claimed in claim 3, wherein the switch circuit (106) comprises:
a capacitor (164) coupled to a cathode terminal of the diode (162) and the ground terminal of the voltage terminal; and
a Schottky diode (166) coupled to the anode terminal of the diode (162) and the ground terminal of the voltage source (102).

6. The AC control circuit (100) as claimed in claim 3, comprising:
a controller having a digital input pin D0 connected to the output terminal and adapted to receive the output signal, wherein the controller is adapted to deactivate a compressor of the HVAC unit based on the receipt of the output signal;
a Zener diode (174) having a cathode terminal connected to the output terminal (146) and the digital input pin D0; and
a capacitor (176) having a terminal connected to the output terminal (146) and the digital input pin D0, and another terminal connected to the ground terminal.

7. The AC control circuit (100) as claimed in claim 6, wherein the knob (114) is adapted:
assume a zero position wherein the knob (114) is disconnected from the resistor units (110) and the non-inverting voltage (172) is greater than inverting voltage (160);
assume a first position wherein the knob (114) is connected to the resistor (126) and value of a value of electrical resistance is submission of resistance values of Blower resistance, resistors (126, 128, and 130), and wherein the non-inverting voltage (172) is lower than inverting voltage (160);
assume a second position wherein the knob (114) is connected to the resistor (128) and value of a value of electrical resistance is submission of resistance values of Blower resistance, resistors (128) and (130), and wherein the non-inverting voltage (172) is lower than inverting voltage (160);
assume a third position wherein the knob (114) is connected to the resistor (130) and value of a value of electrical resistance is equal to a resistance value of Blower resistance, resistor (130), and wherein the non-inverting voltage (172) is lower than inverting voltage (160); and
assume a fourth position wherein the knob (114) is connected to the negative terminal of the blower fan and wherein the non-inverting voltage (172) is lower than inverting voltage (160),
wherein the OP AMP (136) is adapted to generate the output signal in the zero position.