Electric automobile PTC control integrated heating system and control diagnosis method

Abstract

The invention discloses an electric automobile PTC control integrated heating system and a control diagnosis method, and belongs to the technical field of automobile electronics. According to the system, a PTC control driving module, a current sensor, a chip temperature sensor and an IGBT are integrated in a motor control unit MCU, and a traditional external high-voltage relay scheme is replaced. Through receiving a target temperature signal, the MCU calculates the required heating power in real time, and employs a PWM signal to drive the IGBT, thereby achieving the power adjustment of the PTC heater. The system integrates a current sensor and a temperature sensor, cooperates with the temperature feedback of an HVAC built-in temperature sensor, forms closed-loop control, has the functions of real-time diagnosis and overcurrent and over-temperature protection, and effectively prevents dry burning. According to the invention, the hardware cost is reduced, the energy consumption is optimized, and the system reliability is improved.

Description

Technical Field

[0001] This invention belongs to the field of automotive electronics technology. Specifically, this invention relates to a heating system and control diagnostic method for electric vehicles with integrated MCU and PTC control. Background Technology

[0002] In recent years, with increasingly fierce competition in the A00-class pure electric vehicle market and ever-higher requirements for cost control, the development of electric drive systems has been rapidly advancing towards higher speeds, higher voltages, and greater integration. From 2-in-1 to 3-in-1 and then to multi-in-one integration, the integration of electronic technology and mechanical structures can be further improved, resulting in a better cost-performance ratio for electric drive systems.

[0003] Currently, the HVAC systems in A00-class pure electric vehicles on the market use a PTC (Power Transmission Control) system with external VCU (Vehicle Control Unit) controlling relay settings to adjust the PTC heating power. As electric vehicles increasingly demand integrated and low-cost solutions, the design of integrating the PTC control unit into the MCU (Microcontroller Unit) is a future trend. Integration refers to integrating the PTC control unit into the MCU, with the heating element integrated internally within the HVAC system, and using PWM (Pulse Width Control) to adjust the power in real-time to match the vehicle's heating needs.

[0004] Patent No. (CN202211697661) discloses a relay-based safety control system for a PTC heater, including a high-voltage relay connected in series with the PTC heating element; a temperature control switch installed near the PTC heating element, connected in series in the control circuit of the high-voltage relay coil; and a PTC main controller connected to the high-voltage relay for control. This invention achieves low-cost series control of the PTC heating element by using a high-voltage relay at the power supply end of the PTC heating element. When the PTC heating element receives a heating request, the PTC main controller controls the high-voltage relay coil to conduct, the high-voltage relay to engage, and the PTC heating element to receive power. The power of the PTC heating element is adjusted by IGBT control, thus achieving low-cost series control of the PTC heating element.

[0005] The above solution requires an external high-voltage relay and relay box, which leads to a complex system structure, increased costs, and a limited lifespan for the relays. It is also prone to problems such as electric arcing during switching. The control method of this solution is also relatively simple, unable to form a closed-loop control, unable to be optimized and adjusted in real time according to actual working conditions, lacks a sound fault diagnosis mechanism, and poses safety hazards. Summary of the Invention

[0006] The purpose of this invention is to provide an integrated heating system with PTC control for electric vehicles and a control diagnostic method to solve the problems of high system cost, low reliability, inflexible power regulation, and inability to achieve closed-loop control in the prior art.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: This invention provides an integrated heating system for electric vehicles with PTC control, including a motor control unit (MCU) and a positive temperature coefficient (PTC) heater. The MCU integrates a PTC control drive module, a current sensor, a chip temperature sensor, and an IGBT. The signal output of the PTC control drive module is connected to the gate of the IGBT, and the collector and emitter of the IGBT are connected in series in the power supply circuit of the PTC heater. The current sensor is connected in series in the power supply circuit of the PTC heater to collect the circuit current. The chip temperature sensor is located inside or on the surface of the MCU to collect the MCU's temperature. The system also includes a built-in HVAC temperature sensor, whose signal output is connected to the signal input of the MCU.

[0008] Furthermore, the motor control unit (MCU) receives signals from the HVAC built-in temperature sensor, current sensor, and chip temperature sensor, and based on the difference between the signal from the HVAC built-in temperature sensor and the target temperature, it outputs a PWM control signal to the bipolar transistor IGBT through the PTC control drive module.

[0009] Furthermore, the PTC control drive module, current sensor, and chip temperature sensor are integrated into the same chip or the same package module of the motor control unit MCU through packaging technology.

[0010] Furthermore, both the HVAC built-in temperature sensor and the chip temperature sensor are negative temperature coefficient thermistors.

[0011] Furthermore, the motor control unit (MCU) communicates with the vehicle controller (VCU) via the CAN bus to receive the positive temperature coefficient (PTC) heater switch signal and the target temperature setpoint.

[0012] This invention also provides a control diagnostic method for an integrated heating system with PTC control in an electric vehicle, comprising the following steps: S1: The system powers on and the motor control unit (MCU) performs a self-test. S2: Receives the positive temperature coefficient PTC heater switching signal and the target temperature T_target setting; S3: Calculate the required heating power P_calculated based on the difference ΔT between the target temperature and the current crew cabin temperature; S4: Determine whether P_calculated exceeds the system's maximum allowable power Pmax. If it does, limit the output power. S5: Output the corresponding PWM control signal based on P_calculated; S6: The PTC heater outputs the actual power P_output based on the PWM signal; S7: Real-time monitoring of the current and temperature of the PTC control loop, determining whether the preset threshold is exceeded, performing fault detection, and executing protection strategies when an anomaly is diagnosed; S8: Dynamically adjusts the PWM output based on the actual temperature T_current in the crew cabin to achieve closed-loop control.

[0013] Furthermore, the motor control unit (MCU) uses a PID algorithm to calculate the required heating power P_calculated, which is calculated as follows: P_calculated = Kp * ΔT + Ki * ∫(ΔT)dt + Kd * d(ΔT) / dt, where ΔT is the difference between the target temperature and the actual ambient temperature.

[0014] Furthermore, the fault diagnosis includes overcurrent diagnosis and overtemperature diagnosis; the overcurrent diagnosis is based on comparing the current value collected by the current sensor with a preset maximum current threshold to determine whether the current value collected by the current sensor exceeds a first preset safety threshold; the overtemperature diagnosis is based on comparing the temperature value collected by the chip temperature sensor with a preset maximum temperature threshold to determine whether the temperature value collected by the chip temperature sensor exceeds a second preset safety threshold.

[0015] Furthermore, protection actions include stopping the PWM signal output or reducing the output power of the PWM signal.

[0016] The electric vehicle PTC control integrated heating system and control diagnostic method of the present invention have the following advantages: (1) The present invention integrates the PTC control drive module, current sensor and chip temperature sensor into the motor control unit MCU, which significantly reduces the number of external components, reduces system cost and size, and improves product competitiveness.

[0017] (2) This invention achieves continuous and precise adjustment of the heating power of the positive temperature coefficient PTC heater by controlling the bipolar transistor IGBT with PWM. It can adjust the output power in real time according to the difference between the actual temperature of the crew cabin and the target temperature, thereby improving the energy efficiency.

[0018] (3) The present invention forms a complete closed-loop control system by using an in-cabin temperature sensor, a current sensor and a chip temperature sensor, thereby realizing precise monitoring and regulation of the heating process.

[0019] (4) The present invention has a complete fault diagnosis mechanism, which can monitor current and temperature parameters in real time and take protective measures in time when abnormalities occur, effectively preventing safety hazards such as dry burning of positive temperature coefficient PTC heaters.

[0020] (5) The present invention uses bipolar transistor IGBT as a power switching device, and with PWM control technology, the system response speed is faster and the control is more flexible than the traditional relay solution. Attached Figure Description

[0021] This manual includes the following figures, which illustrate the following: Figure 1 This is a block diagram of the overall hardware architecture of an electric vehicle PTC control integrated heating system according to the present invention. Figure 2 This is a flowchart illustrating a control and diagnostic method for an integrated heating system based on a PTC control in an electric vehicle, according to the present invention. Detailed Implementation

[0022] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention, and to facilitate its implementation.

[0023] like Figure 1 The electric vehicle PTC-controlled integrated heating system includes a motor control unit (MCU) and a positive temperature coefficient (PTC) heater. The MCU integrates a PTC control drive module, a current sensor, a chip temperature sensor, and an IGBT (Inductively Coupled Transistor). The collector and emitter of the IGBT are connected in series between the high-voltage power supply and the PTC heater core, replacing the original relay contacts. It receives PWM signals from the MCU to switch on and off at high speed, thereby precisely controlling the average current. The signal output of the PTC control drive module is connected to the gate of the IGBT. The current sensor is connected in series in the power supply circuit of the PTC heater to collect the circuit current. A negative temperature coefficient (NTC) thermistor, acting as a chip temperature sensor, is tightly mounted on the heat sink of the IGBT inside the MCU to directly monitor the temperature of the power devices. Furthermore, a second NTC thermistor is installed inside the vehicle's HVAC system as a built-in HVAC temperature sensor to detect the current actual temperature T_current in the passenger compartment.

[0024] All these sensors are connected to the high-precision digital-to-analog converter (ADC) input pin of the MCU through corresponding filtering and amplification circuits. The system's commands originate from the vehicle control unit (VCU), which communicates with the motor control unit (MCU) via the CAN bus, issuing PTC enable commands and the target temperature T_target. The MCU receives signals from the HVAC built-in temperature sensor, current sensor, and chip temperature sensor, and based on the difference between the HVAC built-in temperature sensor signal and the target temperature, outputs a PWM control signal to the IGBT bipolar transistor via the PTC control drive module.

[0025] like Figure 2 The diagram shown is a detailed flowchart of a control and diagnostic method for an integrated heating system based on a PTC control in an electric vehicle, according to the present invention. The specific steps are as follows: S1: The vehicle's high and low voltages are powered on. Subsequently, the motor control unit (MCU) immediately executes a chip self-test. In this step, the MCU's firmware initializes and performs functional checks on its critical peripherals. This includes verifying the integrity of the internal memory, testing whether the ADC module can correctly sample the reference voltage, checking whether the PWM timer channel can output normally, and confirming whether the CAN controller can send and receive messages normally. Simultaneously, it reads the initial values ​​of the current sensor and two temperature sensors to determine if they are within physically possible ranges (e.g., current values ​​near zero amperes, temperature values ​​matching ambient temperature), thereby diagnosing whether the sensors have open or short circuit faults. If any self-test fails, the MCU sends a clear fault code to the vehicle control unit (VCU) via the CAN bus and immediately locks the positive temperature coefficient (PTC) heater, preventing it from starting.

[0026] S2: After passing the self-test, the system enters standby mode, awaiting the user's heating command. When the driver activates the heating function and sets the target temperature via the air conditioning panel, the VCU sends the "PTC switch" signal and the set target temperature T_target to the MCU via the CAN bus. The control process can only continue after the MCU receives this valid command.

[0027] S3: Next, the system enters the heating power calculation stage S3. The MCU first reads the HVAC built-in temperature sensor through the ADC to obtain the current temperature T_current of the passenger compartment. Then, it calculates the difference between the target temperature and the current temperature, ΔT = T_target - T_current. This temperature difference ΔT is input into a discrete PID controller to calculate the theoretically required heating power P_calculated. The specific expression of this PID control algorithm is: P_calculated = Kp * ΔT + Ki * ∫(ΔT)dt + Kd * d(ΔT) / dt. Wherein, Kp is the proportional coefficient, used for rapid response to temperature difference; the larger the temperature difference, the greater the output power. Ki is the integral coefficient, used to eliminate system steady-state error; by accumulating historical temperature differences, it can provide fine adjustment when the temperature approaches the set value, avoiding the presence of a small temperature difference. Kd is the derivative coefficient, which performs predictive adjustment based on the trend of temperature difference changes; when the temperature rises rapidly and approaches the target, it can reduce the power output in advance, effectively suppressing overshoot and temperature fluctuations. Δt is the control period, and ΔT is the difference between the target temperature and the actual ambient temperature. The calculated P_calculated must be compared with the system's preset maximum allowable power P_max, and the smaller value should be taken to ensure that the requested power does not exceed the supply capacity of the PTC heater.

[0028] S4: After calculating the theoretical power requirement P_calculated, the MCU determines whether P_calculated is within a safe output range and decides on the system's subsequent behavior accordingly. First, the system checks the basic rationality of P_calculated: if its value is less than zero, it is considered an invalid calculation result; in this case, the system immediately abandons the current output, jumps directly to the diagnostic monitoring step S7, triggers a high-priority fault code, and enters safety mode to lock the PTC function to prevent malfunction. If P_calculated equals zero, it indicates that heating is not currently required, and the system directly proceeds to step S8 to continuously monitor the cabin temperature. If P_calculated is a valid value greater than zero, the system further checks the capability range by comparing it with the system's preset maximum allowable power Pmax; if it exceeds Pmax, the system will limit the power for hardware protection, setting the final power to Pmax. Finally, only P_calculated values ​​that pass all these checks, are confirmed as valid and within a safe range, will be officially adopted by the system and ready to proceed to the next step.

[0029] S5: Combining the real-time sampled voltage, the corresponding PWM signal duty cycle is determined using an internally pre-calibrated "power-duty cycle" mapping table or calculation formula. Subsequently, the MCU's PWM generator outputs a series of pulse signals at a preset frequency and the calculated duty cycle. This PWM signal, after passing through the PTC control drive module, controls the on / off state of a single IGBT transistor.

[0030] S6: When the IGBT starts operating according to the PWM command, the system enters the actual power output stage. At this time, the current flows through the core of the positive temperature coefficient PTC heater in the form of PWM, causing it to heat up. The actual output power P_output can be calculated using the real-time sampled voltage U and the current I measured by the current sensor, according to the formula P_output = U * I. This value is used for system monitoring and closed-loop feedback.

[0031] S7: The system continuously monitors current and temperature. For current monitoring, the MCU constantly reads the current sensor value I. Once I exceeds the preset maximum safety threshold Imax, the system immediately identifies an overcurrent fault and executes protection operations: instantly shutting down the PWM output and latching the fault state. Simultaneously, the PTC control drive module also acts as a hardware-level rapid protection, enabling short-circuiting of the IGBT within microseconds to achieve hard shutdown. For temperature monitoring: the MCU simultaneously reads its chip temperature sensor T_mcu and the HVAC built-in temperature sensor T_current. If the MCU's internal temperature T_mcu exceeds its maximum allowable junction temperature T_mcu_max, the control system gradually reduces the PWM output duty cycle to decrease heat generation. If the temperature continues to rise, the output is completely shut down to prevent MCU damage due to overheating. If the HVAC outlet temperature T_current exceeds the maximum safe temperature T_max set to prevent PTC dry burning, the system immediately cuts off the PTC power supply.

[0032] S8: The system completes closed-loop regulation. The cabin temperature T_current begins to change under the influence of PTC heating, and the HVAC built-in temperature sensor continuously feeds this change back to the MCU. The MCU compares the latest T_current with T_target again, calculates the new ΔT, and repeats the process from S3 to S6, dynamically adjusting the PWM output. When the cabin temperature is low, the system outputs high power to quickly raise the temperature; when the temperature approaches the target value, the system automatically enters a low-power heat preservation state.

[0033] The electric vehicle PTC control integrated heating system and control diagnostic method proposed in this invention significantly reduce system costs and optimize structure after implementation. Traditional solutions rely on external high-voltage relay boxes, using combinations of multiple relays to achieve a limited number of fixed power levels. This solution completely eliminates this external structure, integrating the PTC control drive module, IGBT (bipolar transistor), current sensor, and chip temperature sensor within the motor control unit (MCU). This integrated design not only saves on the cost of the relays themselves but also significantly reduces related procurement, inventory, assembly, and logistics costs. Simultaneously, the simplified hardware structure reduces the number of connection points and components, improving system production and assembly efficiency and reducing potential failure rates caused by poor external connector contact or relay mechanical failure. This fundamentally reduces costs and increases efficiency, providing a solid foundation for its promotion and application in the extremely cost-sensitive A00-class pure electric vehicles.

[0034] Compared to traditional relay solutions that only offer "on / off" gear control with step-like power output changes and lack smooth adjustment, this solution uses a PWM signal output from an MCU to precisely control the IGBT's on / off state, thereby controlling the PTC heater's power. The system uses a PID control algorithm to calculate the required precise heating power P_calculated in real time based on the difference ΔT between the target temperature and the current actual temperature in the passenger compartment. The heating system can dynamically and smoothly follow changes in the vehicle's heat load. In the initial stage of heating, the system can quickly generate heat at a higher power; when approaching the set temperature, it automatically reduces power to maintain a constant temperature. This "on-demand heating" mode completely avoids the energy waste and temperature fluctuations caused by fixed power and switching cycles in traditional solutions, significantly reducing the PTC's energy consumption of the power battery, thus effectively extending the vehicle's range in winter and improving passenger comfort.

[0035] Furthermore, this embodiment, through high integration and built-in sensors, constructs a real closed-loop diagnostic and safety protection system, greatly improving the system's reliability and safety. The current sensor and chip temperature sensor integrated within the MCU continuously monitor the PTC circuit's operating status. During operation, the system continuously judges key parameters: whether the current is within the safe range (I ≤ Imax), and whether the MCU chip and PTC body temperature exceed the safe threshold (T ≤ Tmax). Once overcurrent, overtemperature, or other abnormalities are detected, the MCU can immediately shut down the PWM output and cut off the IGBT within milliseconds, achieving proactive safety protection. This effectively prevents the risk of "dry burning" caused by fan failure or duct blockage leading to insufficient heat dissipation from the PTC, fundamentally eliminating potential fire hazards. This embedded, intelligent diagnostic function not only improves the overall vehicle safety level but also provides clear fault guidance for after-sales maintenance, shortening troubleshooting time.

[0036] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. An integrated heating system for electric vehicles with PTC control, comprising a motor control unit (MCU) and a positive temperature coefficient (PTC) heater, characterized in that: The motor control unit (MCU) integrates a PTC control drive module, a current sensor, a chip temperature sensor, and a bipolar junction transistor (IGBT). The signal output terminal of the PTC control drive module is connected to the gate of the IGBT, and the collector and emitter of the IGBT are connected in series in the high-voltage power supply circuit of the positive temperature coefficient (PTC) heater. The current sensor is connected in series in the power supply circuit of the PTC heater, and its signal output terminal is connected to the digital-to-analog converter (DAC) sampling port of the motor control unit (MCU). The chip temperature sensor is integrated inside the motor control unit (MCU). The system also includes a built-in HVAC temperature sensor, the signal output terminal of which is connected to the signal input terminal of the motor control unit (MCU), and the PTC heater is connected to the MCU.

2. The electric vehicle PTC-controlled integrated heating system according to claim 1, characterized in that, The motor control unit (MCU) receives signals from the HVAC built-in temperature sensor, the current sensor, and the chip temperature sensor, and outputs a PWM control signal to the bipolar transistor IGBT through the PTC control drive module based on the difference between the signal from the HVAC built-in temperature sensor and the target temperature.

3. The electric vehicle PTC-controlled integrated heating system according to claim 1, characterized in that, The PTC control drive module, the current sensor, and the chip temperature sensor are integrated into the same chip or the same package module of the motor control unit (MCU) through a packaging process.

4. The electric vehicle PTC-controlled integrated heating system according to claim 1, characterized in that, Both the built-in temperature sensor in the HVAC system and the chip temperature sensor are negative temperature coefficient thermistors.

5. The electric vehicle PTC-controlled integrated heating system according to claim 1, characterized in that, The motor control unit (MCU) communicates with the vehicle control unit (VCU) via the CAN bus and receives the positive temperature coefficient (PTC) heater switch signal and the target temperature setpoint.

6. A control diagnostic method for an electric vehicle PTC-controlled integrated heating system according to any one of claims 1-5, characterized in that, Includes the following steps: S1: The system is powered on, and the motor control unit (MCU) performs a self-test; S2: Receives the positive temperature coefficient (PTC) heater switch signal and the target temperature T_target setting; S3: Calculate the required heating power P_calculated based on the difference ΔT between the target temperature and the current crew cabin temperature; S4: Determine whether P_calculated exceeds the system's maximum allowable power Pmax. If it does, limit the output power. S5: Output the corresponding PWM control signal based on P_calculated; S6: The PTC heater outputs the actual power P_output based on the PWM signal; S7: Real-time monitoring of the current and temperature of the PTC control loop, determining whether the preset threshold is exceeded, performing fault detection, and executing protection strategies when an anomaly is diagnosed; S8: Dynamically adjusts the PWM output based on the actual temperature T_current in the crew cabin to achieve closed-loop control.

7. A control diagnostic method for an electric vehicle PTC-controlled integrated heating system according to claim 6, characterized in that, The motor control unit (MCU) uses a PID algorithm to calculate the required heating power P_calculated, and the calculation formula is: P_calculated = Kp * ΔT + Ki * ∫(ΔT)dt + Kd * d(ΔT) / dt, where ΔT is the difference between the target temperature and the actual ambient temperature.

8. A control and diagnostic method for an integrated heating system with PTC control in an electric vehicle according to claim 6, characterized in that, The fault diagnosis includes overcurrent diagnosis and overtemperature diagnosis; the overcurrent diagnosis is based on comparing the current value collected by the current sensor with a preset maximum current threshold to determine whether the current value collected by the current sensor exceeds a first preset safety threshold. The over-temperature diagnosis is based on comparing the temperature value collected by the chip temperature sensor with a preset maximum temperature threshold to determine whether the temperature value collected by the chip temperature sensor exceeds a second preset safety threshold.

9. A control and diagnostic method for an integrated heating system with PTC control in an electric vehicle according to claim 6, characterized in that, The protection actions include stopping the PWM signal output or reducing the output power of the PWM signal.

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