Description:Field of Invention
The present invention relates to the field of positive temperature coefficient (“PTC”) heaters and specifically relates to a control system of the PTC heaters intended for use in vehicle air conditioning systems, with a primary focus on electric propulsion vehicles. The present invention ensures efficient regulation of the PTC Heater and comfortable cabin temperature control in electric vehicles.

Background of the Invention
In conventional vehicles, a significant portion of the heat produced during engine operation is considered waste heat. This waste heat is repurposed to heat the vehicle's cabin using a heat exchanger that transfers heat from the engine coolant to the cabin air. However, in electric vehicles, there is no internal combustion engine and propulsion is primarily provided by electric motors. Consequently, they do not produce waste heat during operation. Due to the absence of waste heat, electric vehicles face challenges in providing sufficient cabin heating to ensure user comfort and defrosting, particularly in cold weather conditions. To address this challenge, electric vehicles use separate heating elements, such as electric resistance heaters or positive temperature coefficient heaters, specifically designed to generate heat for cabin heating without relying on the waste heat from an engine. PTC heaters work by directly heating the air in the vehicle cabin through a resistive heating element, ensuring effective and controlled cabin temperature management in electric vehicles.
In the context of PTC heaters, "non-linear behavior" refers to the property of these heating elements where their electrical resistance increases significantly as their temperature rises. This non-linear behavior is a distinctive characteristic of PTC heaters and is quite different from conventional resistive heating elements, which typically exhibit linear resistance (the resistance remains relatively constant with temperature changes). The non-linear behavior of PTC heaters is advantageous in certain applications because it allows them to be self-regulating. When the temperature of the heater rises, its resistance increases, which, in turn, reduces the flow of electrical current through it. This self-regulating property helps prevent overheating and makes PTC heaters a popular choice for various applications, including automotive heating systems, as they can provide consistent and safe heating.
In modern electric vehicles, the electronic control unit (“ECU”) plays a central role in regulating and optimizing the operation of a PTC heater. The ECU integrates with the overall climate control system. It translates user-set temperature preferences and commands into specific control signals for the PTC heater, allowing users to customize their comfort levels easily. It coordinates the PTC heater's operation with other components, such as the blower fan, air conditioning, and ventilation, to provide a comfortable and well-distributed cabin environment. Its primary responsibilities encompass monitoring and regulating the PTC heater's performance to optimize cabin heating while considering energy efficiency and user comfort. The PTC heater ECU constantly assesses variables such as cabin temperature, external conditions, and user preferences through a network of temperature sensors and input controls. Based on this information, it modulates the power supplied to the PTC heater to achieve the desired interior temperature.
When the ECU is not designed properly, it can give rise to a multitude of problems that can significantly impact the performance and safety of the heating system in a vehicle. Inefficient ECU control can lead to suboptimal heating, resulting in energy wastage, reduced vehicle range in electric vehicles, and higher operational expenses. Poor temperature regulation may cause discomfort for users, compromising their overall experience, and potentially leading to safety concerns if extreme temperatures are reached. Additionally, inadequate diagnostics, reliability issues, and complexity in repairs can further exacerbate these problems, potentially leading to costly retrofits or replacements. Therefore, proper design and testing of ECUs are essential to ensure the reliable and efficient operation of systems in electric vehicles.
The present invention recognizes the importance of an effective control system and provides a reliable control unit with additional protection features to regulate the PTC heater in electric vehicles and protect its related components from safety hazards that occur during abnormal conditions. The present invention employs a proportional integral derivative (“PID”) controller with constant power control management for a PTC heater, which plays a crucial role in maintaining the desired cabin temperature. By controlling the current flowing through the PTC heater, it finely tunes the temperature, providing a means to achieve and maintain the desired climate inside the cabin. This method offers a practical way to control cabin temperature using the PTC heater, primarily relying on a blower to distribute heated air and adjusting the temperature by modulating the current flow, ensuring user comfort and efficiency. The present invention provides an ECU that has inbuilt diagnostic functions that continually check for irregular conditions or faults within the system. The present invention provides a control system with auto-recovery processes. Once a fault is detected and identified, the system can take corrective actions automatically to restore normal operation.
Various prior arts have disclosed similar control methods and devices to regulate PTC heaters:
There are several existing control methods for PTC heaters in electric vehicles, that lag in response time and result in temperature control delays. Control methods with slower response times may result in overshooting the desired temperature, leading to energy wastage as the system attempts to stabilize. The present invention provides current-based control which allows for rapid adjustments to the PTC heater's output. When users change the duty cycle to modify the desired temperature, the system responds quickly, reducing the time it takes to reach the new setpoint. In addition, the existing control system is lacking in diagnostic capabilities and may not provide the appropriate degree of safety for the heating system. The absence of diagnostic features in the existing PTC heater control system is a notable limitation. The present invention addresses this limitation and builds a control system with protection features with the ability to diagnose anomalies or irregular conditions and safeguard against potential hazards.
Chinese patent application CN106252789A describes a PTC heater and integrated control system consisting of a heater and radiator. In this prior art, the heater is located within a housing and features at least one temperature sensor and a ground wire. The cooling system provided by the radiator comprises a fluid container with an inlet and outlet or is integrated with fins on the heater matrix. The control system comprises a controller that connects to various modules, including temperature collection, insulation monitoring, switch drive, voltage acquisition, current acquisition, and control and supply terminals. Whereas, the present invention has a proportional integral derivative controller with a constant power method, ensuring comfortable and efficient heating within the vehicle cabin. Moreover, the present invention incorporates an array of sensors to collect real-time data, including temperature, voltage, and current measurements, enabling precise adjustments to the heating power for maintaining the desired cabin temperature. The feature of detecting HV link sensor failure is not present in this instant prior art. Also, the present invention employs a 4kW power rating of the PTC heater, indicating its capacity to provide significant heating, particularly in colder weather conditions.
US patent application US20230068735 discloses an air conditioning control system for an electric vehicle, includes a heating, ventilation, and air conditioning body, an evaporator provided in the HVAC body, a PTC heater, an input unit for receiving set temperature of each of a driver's seat and a user's seat, left and right temperature sensing units of sensing an air temperature passing through a left side and a right side of the PTC heater, a control unit of outputting a control signal for controlling the PTC heater based on the set temperature input from the input unit and a measurement temperature measured from each of the left and right temperature sensing units, and a power supply unit of adjusting the power supplied to the PTC heater according to the output PWM control signal of the control unit. It is noteworthy that the present invention’s control system regulates the power / current consumption of the PTC heater based on a constant power algorithm.
The temperature of the PTC heater is controlled based on the PWM duty cycle. In this prior art, there are no protection circuits to prevent the potential hazards that may occur during abnormal conditions. The present invention is equipped with a protection device including a thermistor to detect and respond to high temperatures, and under or high voltages through cut-off methods. Further, the present invention also includes diagnostic capabilities to detect defects in the HV link sensors. This allows for early identification of sensor issues and ensures the proper functioning of the heating system which is absent in this prior art.
To solve the above-mentioned limitations of the prior arts, the present invention has a control system with integrated diagnostic functions, as described in the previous context, overcomes these limitations by proactively monitoring the system's health, detecting issues early, and allowing for prompt corrective actions. The present invention uses a proportional integral derivative controller to refine temperature regulation by incorporating a derivative term. It anticipates future temperature changes, reducing overshooting and oscillations. Controlling the current flowing through the PTC heater core dynamically is an effective approach to reduce delays in controlling the PTC heater and achieving precise and responsive temperature regulation. By adjusting the current in real time based on temperature feedback, the ECU can maintain the desired cabin temperature efficiently and with minimal lag.
Furthermore, the present invention has embedded protection features that contribute to the overall safety, reliability, and longevity of the PTC heating system and its related components, ensuring that they operate safely and efficiently in various conditions, including extreme temperatures and electrical events. This not only improves reliability and safety but also reduces downtime and maintenance costs, making it a more robust and efficient solution. Without proper diagnostics, it can be challenging to detect and address potential issues that may arise during the operation of the PTC heater. This advanced feature goes beyond basic temperature control, making it a sophisticated and forward-thinking solution for managing PTC heaters, especially in applications where safety and performance are critical. This additional layer of intelligence empowers the system to swiftly identify and respond to potential problems. Through continuous evaluation of the system's status and performance, it can take preemptive actions to rectify faults or malfunctions, thereby mitigating the risk of damage, safety concerns, and unforeseen system breakdowns.
Objects of the Invention:
The main object of the present invention is to provide a system and method for controlling the temperature inside the vehicle’s cabin for user comfort.

The primary object of the present invention is to integrate proportional integral derivative controller-based constant power control management that keeps the cabin at a desired temperature.

It is another object of the present invention to achieve precise temperature control inside the vehicle's cabin, ensuring that the temperature remains within the set range without overheating or excessive cooling.

It is another object of the present invention to optimize energy usage by employing the power control management system to regulate the PTC heater’s power output, thereby reducing energy wastage, and promoting energy efficiency.

It is another object of the present invention to operate on high voltage to ensure heating demands are met on a cold day.

It is another object of the present invention to identify overheating, under or over-voltage, and to initiate over-temperature cutoff and under (or) over-voltage cutoffs.

It is another object of the present invention to implement the auto-recovery mechanism that ensures the system can automatically recover and resume normal operation after an issue, such as over temperature or over/under voltage, has been detected and resolved.

It is another object of the present invention to detect and identify open circuit thermal sensors of heaters and other electrical faults that could potentially lead to hazardous situations.

It is another object of the present invention to detect and respond to potential open or short circuits of insulated gate bipolar transistors.

It is another object of the present invention to diagnose HV link sensor defects for any sensor issues and ensure the proper functioning of the heating system which ensures the safe operation of the PTC heater.

It is another object of the present invention to detect the over-current feedback of each switching device and cut off the IGBT current above the predefined current measurement.

Summary of the Invention
The present invention offers an improved PTC heater control system using a proportional integral derivative controller-based constant power management, addressing conventional issues. The system integrates components like the LIN (“Local Interconnect Network”) transceiver, microcontroller, IGBT (“Insulated Gate Bipolar Transistor”), IGBT gate driver, PTC Heater, and air blower to efficiently manage cabin heating in vehicles. LIN is a communication protocol used in automotive applications. The LIN transceiver facilitates communication between the master electric vehicle controller (“EVC”) and the PTC electronic control unit for command exchange and data transfer. The microcontroller plays a central role in the system. It converts the demanded duty cycle into constant power and then compares it with the actual power of the PTC heater. The microcontroller checks sensor data (including temperature, high voltage, and high current sensors), and sends PWM control signals with 120-degree phase shifts to the IGBT gate drivers, ensuring even power distribution among three heater cores. The IGBT gate driver is responsible for controlling the power supplied to the PTC heater accordingly. PTC heater heats up based on the power supplied to it by the IGBT gate driver. An air blower is used to circulate air into the vehicle cabin through the PTC heater core. This allows the heated air to be distributed throughout the cabin, providing comfort and warmth to the occupants.
The present invention provides a 4kW power rating, which indicates the heating capacity of the PTC heater. This level of power is well-suited for rapidly and effectively heating the cabin space, even in colder weather conditions. The present invention is designed to handle high voltage capacity, which is essential in electric vehicles where high voltage systems are prevalent. As the cabin temperature approaches the desired setpoint, the PTC heater automatically reduces its power output, preventing overheating and unnecessary energy consumption. This feature helps in conserving energy and optimizing the overall efficiency of the heating system.
The present system discloses features to safeguard against potential issues such as overheating, electrical faults, and electronic malfunctions. This ensures safe and reliable operation even under adverse conditions. The present system is equipped with protection circuits to detect and respond to high temperatures, and high or low voltages through cut-off methods. Further, the present invention also provides open or short circuit protection that may occur in the PTC heater. The present invention also includes diagnostic capabilities to detect defects in the HV link sensors. This allows for early identification of sensor issues and ensures the proper functioning of the heating system. These protections prevent any hazards and ensure the system operates safely under various conditions. The present system is also equipped with a current measurement facility to monitor and measure the electric current flowing through the PTC heating element. The power control management system can calculate the actual power being delivered to the PTC heater by knowing the current consumption. This information enables the system to optimize energy usage and modify the power output as needed to efficiently maintain the appropriate temperature in the cabin.
Brief Description of the Drawings
Figure 1 illustrates a conceptual block diagram of the PTC heater control system in accordance with the present invention.
Figure 2 illustrates the flowchart that outlines the process of PTC heater control system in an electric vehicle in accordance with the present invention.
Figure 3 illustrates the pulse width modulation control signals input to switch the PTC heater cores in accordance with the present invention.
While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of examples in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concept of the term appropriately to describe their own invention in the best way. The present invention should be construed as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, it should be understood that equivalents and modifications are possible.
Detailed Description of the Invention with Respect to the Drawings
The present invention as embodied by the “A system and method for controlling positive temperature coefficient heaters in electric vehicles” succinctly fulfills the above-mentioned need(s) in the art. The present invention has an objective(s) arising as a result of the above-mentioned need(s), said objective(s) being enumerated below. In as much as the objective(s) of the present invention are enumerated, it will be obvious to a person skilled in the art that, the enumerated objective(s) are not exhaustive of the present invention in its entirety and are enclosed solely for the purpose of illustration. Further, the present invention encloses within its scope and purview, any structural alternative(s) and/or any functional equivalent(s) even though, such structural alternative(s) and/or any functional equivalent(s) are not mentioned explicitly herein or elsewhere, in the present disclosure. The present invention therefore encompasses also, any improvisation(s)/ modification(s) applied to the structural alternative(s)/functional alternative(s) within its scope and purview. The present invention may be embodied in other specific forms (s) without departing from the spirit or essential attributes thereof.

Key definitions:
EVC – Electric Vehicle Controller through which the user sets the desired temperature in the cabin of the electric vehicle.
ECU – Electronic Control Unit
PTC – Positive Temperature Coefficient
IGBT – Insulated Gate Bipolar Transistors used to switch between on and off states based on the voltage.
PWM – Pulse Width Modulation
LIN – Local Interconnect Network
HV link – High voltage link
The present invention provides a system and method for controlling the PTC heater to provide effective heat inside the vehicle cabin. The present invention comprises multiple IGBTs that are employed as a switching device to lower the input power to the PTC heater core because each core rating is greater than 4KVA. The ECU controls the IGBT based on the temperature setting assigned by the user in the dashboard. Thermistors detect temperature and protect the heater core and IGBT from overheating. All processing of instrument PTC ECU functions is handled by a microcontroller. The microcontroller contains analog and digital interfaces required by the PTC ECU to interface with the rest of the vehicle. The system assumes the operating conditions of - 40°C to + 85°C ambient for the PTC ECU.
In the preferred embodiment of the present invention, wherein a system involving various components and processes for controlling a PTC heater within a vehicle cabin is disclosed. Some of the key elements are the LIN transceiver, microcontroller, IGBTs, IGBT gate driver, PTC Heater, and air blower; wherein the LIN transceiver is responsible for receiving command signals from the master electric vehicle controller to the PTC electronic control unit. It also transmits acquired data from the PTC ECU back to the EVC. The microcontroller receives the demanded power from the master EVC, indicating the desired heating level. It then compares acquired data from various sensors, including thermistors (temperature sensors), high voltage sensors, high current sensors, and sensors monitoring the high voltage link. Based on this data, the microcontroller generates control signals that are sent to the IGBT gate driver. The IGBT gate driver is responsible for controlling the power to the PTC heater. It receives the control signals from the microcontroller and regulates the power supplied to the PTC heater accordingly. An air blower is used to circulate air into the vehicle cabin through the PTC heater core. This enables the heated air to be spread throughout the cabin, giving the users comfort and warmth.
In the preferred embodiment of the present invention, wherein the key features of the PTC heater control system as seen in Fig. 1, comprise the following:
1. 3 PWM Outputs – Heater CORE1, CORE2, CORE3 - % Duty Setting from Master EVC.
2. 2 Analog outputs – Heatsink and Core temperature Inputs for Temperature cut-off.
3. 3 Analog outputs – Heater current sensing input for Master EVC LIN message feedback.
4. 1 Analog output – High voltage bus sensing input for under and over-voltage cut-off.
5. 1 Digital output – High voltage connector interlock input for interface validation
cut-off.
When the users set the desired temperature and are taken into record in terms of the duty cycle in the master EVC. Then the master EVC transmits the user’s temperature request through LIN communication (1) to the PTC Heater ECU. PTC heater ECU will get the power from an e-vehicle low-voltage battery. Components such as the microcontroller (8), LIN transceiver (10), and IGBT gate driver (9) receive power from the low-voltage battery through a DC-DC converter (7).
In the preferred embodiment of the present invention, wherein the microcontroller (8) performs the following checks and methods:
a) checks the high voltage link terminal connection (2).
b) monitors high-voltage levels within specified under and over-voltage limits (5).
c) measures the temperature of the heater core and IGBT heat sink within a limit using thermistors (6).
d) checks the thermal sensor, IGBT open circuit, and short circuit.
After all these checks, the microcontroller converts the demanded duty cycle into constant power and compares the demanded power with the actual power of the PTC heater(4).
The microcontroller calculates the actual power of the PTC heater (4) based on high-voltage measurements, from the high-voltage terminal (5) using a signal conditioner, and the total current of all three PTC heater cores (4) is measured using a current sense shunt resistor and corresponding signal conditioner. Then, these parameters are correlated to the actual power of the PTC heater(4). The Controller (8) compares the demanded power with the actual power of the PTC heater (4). Based on the constant power method, the controller (8) takes the corrective action and sends the corresponding control signal to the IGBT gate drivers(9) in the form of a PWM duty cycle with a 120-degree phase shift. The three IGBT gate drivers(9) drive the 3 IGBTs based on the duty cycle with different phase shifts, which allows the PTC heater to operate effectively.
In the preferred embodiment of the present invention, wherein the flowchart as seen in Fig. 2, illustrates the step-by-step process of the working of the PTC heater control system in an electric vehicle as described hereunder.
The present invention enables the user to set their desired temperature on the master EVC, which is then transmitted to the PTC heater ECU via LIN Communication. Once the ECU receives the request, the microcontroller performs initial checks to ensure safety and functionality, including inspecting high-voltage connections and monitoring over/under voltage, temperature, current, and other electronic defects. After all checks are verified and cleared, the microcontroller calculates the demanded power based on the input duty cycle and compares it to the actual power generated by the PTC heater. It then sends the control signal to IGBT gate drivers in the form of a duty cycle to maintain the demanded power. IGBT gate drives switch the IGBTs to turn on the PTC cores in 120-degree phase shifts. Subsequently, the PTC heater generates heat, and the generated heat gets transferred to the vehicle cabin through the air blower. Thus, the whole process ensures a comfortable and controlled cabin temperature in the electric vehicle, while the PTC heater consistently provides the heat needed to meet the user's temperature request.

Example
The provided example illustrates a scenario involving a control system for a resistive positive temperature coefficient heater in an electric vehicle. Here's a breakdown of the steps and processes outlined in the example:
Master demanded a duty cycle of 25%
25% of the duty cycle will be 25% of 4kW power i.e., 1Kw.
Hence, the demanded power will be 1kW.
To achieve the demanded power, the system considers a high voltage of 250 V (which may vary while the vehicle is in operation). Using the formula P = V x I, the required current to reach the demanded power of 1 kW is calculated as 4A.
Initially, the actual current will be zero. The controller sends the maximum duty cycle to the heater to initiate the heating process. In ambient temperature conditions, the PTC heater's resistance is lower, causing it to draw more current initially. The controller responds by decreasing the pulse width modulation signal, effectively controlling the power supplied to the heater. As the PTC heater’s temperature rises, its resistance increases, leading to a decrease in current flow. Consequently, the controller adjusts the PWM signal to maintain the desired temperature level, ensuring the PTC heater operates efficiently and reaches a stable temperature.
This above example demonstrates how the control system intelligently manages the PTC heater's power and temperature to achieve precise heating control, especially considering variations in voltage and the resistance characteristics of the heater. This approach contributes to effective cabin temperature management in electric vehicles, optimizing both comfort and energy efficiency.
Table 1 illustrates how LIN communication emphasizes the allocation of specific bytes within the LIN frame to various parameters, along with their corresponding cut-off and
auto-recovery conditions.
- Byte 1 serves as a status byte, with each bit dedicated to different tasks such as indicating over-current, over-temperature, and over-voltage conditions.
- Byte 2 is allocated for reporting the total current measurement.
- Byte 3 holds status flags for cabin response errors, high voltage interlock, and IGBT short circuit detection.
- Byte 4 is reserved for communicating the watt power status which indicates the actual power of the PTC.
The remaining bytes within the frame are reserved for potential future functionalities or other specific purposes, optimizing the LIN communication protocol for efficient and organized data exchange between the EVC and various ECUs in the electric vehicle.
The EVC transmits the message to PTC ECU using the bits and bytes allocated within the LIN communication frame. Each bit and byte is allocated to carry the specific information, as outlined in the following table.
TABLE 1: LIN FRAME ALLOTMENT
LIN FRAME VARIABLE NAME CUT OFF RECOVERY
BYTE BIT RANGE
1 Bit 0 Electronics defect indication (Over-current) More than 42A Less than 1A
1 Bit 1 Maximum Power Status (Reserved for future development)
1 Bit 2 Over-temperature (Core) 95 °C 85 °C
Bit 2 Over-temperature (Heat sink) 85 °C 70 °C
1 Bit 3 Under-voltage 148V 168V
Bit 3 Over-voltage 350V 305V
1 Bit 4 Heater Circuit 1 ON/OFF
(IGBT 1 current) More than 16A
Less than 1A

1 Bit 5 Heater Circuit 2 ON/OFF
(IGBT 2 current) More than 13A
Less than 1A

1 Bit 6 Heater Circuit 3 ON/OFF
(IGBT 3 current) More than 13A
Less than 1A

1 Bit 7 Heater Circuit 4 ON/OFF (Reserved for future development)
2 Bit 0-7 Total current measurement 0-42A
3 Bit 0 Cabin Response Error Indication of LIN frame missing
3 Bit 1-2 High Voltage Interlock Open or close status
3 Bit 3 IGBT Short Circuit Detection Fault detected (1) or No fault detected (0)
4 - Watt Power Status Actual power Indication

The prominent features of the present invention are the following:
a) Controller management system: The present invention integrates proportional integral derivative controller-based constant power control management to regulate the current flowing through the PTC heater to maintain the desired temperature set by the user.
b) Thermal Cutoff: The present invention incorporates a thermal cutoff system to detect over-temperature conditions, enabling early detection of overheating and facilitating prompt intervention and automatic recovery processes.
c) Under/Over Voltage Protection: The present invention features an over-voltage protection system that safeguards the ECU and its related components from voltage spikes or surges caused by electrical faults or external factors. This system involves voltage monitoring and the ability to disconnect or isolate the system if voltage levels exceed safe limits. This protection is crucial for preventing damage to sensitive electronic components and enabling auto-recovery processes.
d) Electronics Defects Sensor: The present invention enables detection of the Open circuit of Thermal Sensors of the heater and the Open circuit/short circuit of the insulated Gate Bipolar Transistor.
e) Detection of failure in high voltage link: The present invention enables detecting failures in high link sensors, ensuring the integrity of sensor functionality. This feature is essential for maintaining the safe operation of the PTC heater and the overall heating system.
f) Detection of over-current feedback of each switching device: This feature involves using sensors to monitor the current in a circuit and triggering an alert or shutdown if the current exceeds a safe threshold. It's crucial for preventing damage to electrical components and ensuring safety.
g) 3 Cores switching ON with different phase shifts: This feature pertains to controlling three electrical cores (heating elements) in a way that they turn on/off at 120 degrees with different phase shifts.
h) Indication with LIN message missing: The present invention includes a feature that involves monitoring a Local Interconnect Network (LIN) communication system and raising an alert if an anticipated message isn't received within a specified timeframe.
i) Various applications: The present invention can be adapted for use in high-power and high-voltage applications, expanding its versatility and applicability beyond its original design.
Results and Discussion
Testing the control system of the PTC heater with constant power control management
During the testing phase, the system's power control management system demonstrated precise temperature control, efficiently maintaining the desired cabin temperature for user comfort while optimizing energy consumption. The system's reliability, safety, and energy efficiency make it a valuable addition to the electric vehicle's temperature control system. Additionally, the heater's self-regulating behavior, high voltage compatibility, and potential integration with various protection and diagnostic features make it a valuable component in modern electric vehicles. PTC heaters inherently exhibit self-regulating characteristics, and when combined with a constant power control system, this behavior ensures that the heater operates within safe temperature limits without the risk of overheating. Overall, the integration of a 4kW PTC heater with a PID controller in the e-vehicle provides a high level of comfort and safety for users while optimizing energy usage and overall vehicle performance. The control system’s ability to regulate the PTC heater's power output ensures efficient heating while maintaining precise and consistent temperature control, enhancing the overall driving experience and user satisfaction.
Although the proposed concept has been described as a way of example with reference to various models, it is not limited to the disclosed embodiment, and alternative designs could be constructed without deviating from the scope of the invention as defined above. It will be apparent to a person skilled in the art that the above description is for illustrative purposes only and should not be considered as limiting. Various modifications, additions, alterations, and improvements without deviating from the scope of the invention may be made by a person skilled in the art. , Claims:We Claim:
1. A system for controlling the positive temperature co-efficient heater with constant power control management in an electric vehicle (EV), comprising of:
a. A master electric vehicle controller (EVC) through which the user sets the desired temperature within the cabin of a vehicle;
b. A microcontroller (8), which analyses the sensor data of the vehicle;
c. A Plurality of PTC heater cores (H1, H2, H3);
d. A plurality of insulated gate bipolar transistors (IGBT) (3) is provided, which serve as a switching device for the PTC heater cores;
e. IGBT gate drivers (9), provided with 120-degree phase shifts to drive the insulated gate bipolar transistors (3);
f. An electronic control unit (ECU) that controls IGBT based on the temperature setting assigned by the user within the vehicle;
g. A LIN transceiver (10), which enables data transfer and command exchange between the master electric vehicle controller (EVC) and the PTC electronic control unit (ECU);
h. A DC-DC converter (7) which supplies power to the microcontroller (8), LIN receiver (10), and IGBT gate drivers (9) from the terminal for battery voltage and LIN communication (1),
wherein the terminal for battery voltage and LIN communication (1) is provided, from which power is supplied to the microcontroller (8), the LIN receiver (10), and IGBT gate drivers (9) through DC-DC converters (7).
2. The system as claimed in claim 1, wherein the microcontroller (8) checks a high voltage link terminal connection (2) for detection of the open/close circuit of a HV link.
3. The system as claimed in claim 1, wherein the microcontroller (8) monitors the voltage across the terminal for a high-voltage battery (300V DC) power source (5) and checks whether the voltage is under/over the predetermined limits.
4. The system as claimed in claim 1, wherein the microcontroller (8) monitors the temperature of the PTC heater core and IGBT heat sink terminal (6) using thermistors and determines whether the temperature exceeds predetermined limits.
5. The system as claimed in claim 1, wherein the microcontroller (8) contains analog and digital interfaces required by the PTC ECU to interface with the rest of the vehicle.
6. The system as claimed in claim 1, wherein a terminal for PTC heater cores (4) is provided, from which a corresponding IGBT (3) via IGBT gate drivers (9) turns on the PTC heaters.
7. A method for controlling the positive temperature co-efficient heater with constant power control management, comprising the steps of:
a. The user sets the desired temperature on the master EVC which is transmitted to the PTC heater ECU;
b. the microcontroller (8) receives the LIN feedback signals (analog output) and performs initial checks;
c. the microcontroller (8) calculates the actual power of the PTC heater (4) based on high-voltage measurements, from the high-voltage terminal (5) using a signal conditioner;
d. the total current of all three PTC heater cores (4) is measured using a current sense shunt resistor and corresponding signal conditioner;
e. the microcontroller (8) compares the demanded power with the actual power of the PTC heater (4);
f. the microcontroller (8) sends the corresponding control signal to the IGBT gate drivers (9) in the form of a PWM duty cycle with a 120-degree phase shift;
g. subsequently the PTC heater generates heat, which is transferred to the vehicle cabin through the air blower;
h. if the microcontroller (8) detects the over-current feedback of each switching device, then the microcontroller (8) cuts off the IGBT current above the predefined current measurement, wherein the IGBT gate drivers (9), drive the insulated gate bipolar transistors (3) based on the PWM control signal received from PTC ECU.
8. The method as claimed in claim 7, wherein the high voltage bus detecting circuit continuously monitors the voltage level on the bus and sends the feedback signals (analog output) to the microcontroller (8), which cuts off the voltage supply if the voltage falls below or exceeds specified limits.
9. The method as claimed in claim 7, wherein the microcontroller (8) receives feedback signal (digital output) from the high voltage connector interlock for the interface validation cut-off.
10. The method as claimed in claim 7, wherein the microcontroller (8) checks the temperature of the heater core (4) and heater sink (6) and cuts off the voltage supply if the temperature exceeds the specified limits.
11. The method as claimed in claim 7, wherein if an anticipated message is not received within a predefined amount of time, the LIN indicator raises an alert.