Vehicle Air Conditioner Heater Control With Isolated Temperature Sensing
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Solution Overview
Problem
The existing vehicle-mounted air conditioner control devices face a challenge in securing sufficient electrical insulation and withstand voltage between the low-voltage and high-voltage system circuits, particularly due to the placement of water temperature sensors that are attached to a housing frame serving as ground for the low-voltage system circuit, which can compromise insulation when in the high-voltage system circuit.
Innovation Solution
Incorporating a water temperature sensor in the low-voltage system circuit that outputs a voltage signal, a V/f conversion unit to convert this signal into a frequency signal, and a digital isolator to transmit this frequency signal to the microcontroller in the high-voltage system circuit, maintaining electrical insulation and allowing the microcontroller to control the PTC heater effectively while monitoring temperature and voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the water temperature sensor is disposed in the high-voltage system circuit along with the microcontroller, then the temperature detection function is achieved, but the withstand voltage between the water temperature sensor and the housing frame (ground of low-voltage system circuit) cannot be sufficiently secured
Solution Approach 1:
The system is divided into two separate circuits: the high-voltage system circuit containing the microcontroller and PTC heater, and the low-voltage system circuit containing the water temperature sensor. This segmentation allows temperature detection while maintaining electrical insulation safety, as each circuit operates at its appropriate voltage level with the housing frame serving as ground only for the low-voltage circuit.
2Measurement precision
If the water temperature sensor is attached to the housing frame that serves as ground for the low-voltage system circuit, then the sensor can detect water temperature, but the electrical insulation between high-voltage and low-voltage circuits is compromised
Solution Approach 1:
The water temperature sensor is exclusively placed in the low-voltage system circuit and connected to the low-voltage ground (housing frame), while the microcontroller in the high-voltage circuit receives temperature information through isolated communication channels. This segmentation maintains both measurement precision and electrical insulation reliability.
3Reliability
If a dual microcontroller implementation is used (one in each voltage system), then electrical insulation is maintained, but the device complexity and cost increase
Solution Approach 1:
The water temperature sensor is extracted from the high-voltage system circuit and placed in the low-voltage system circuit. This extraction eliminates the need for a dual microcontroller configuration, as the single microcontroller in the high-voltage circuit can receive temperature data through isolated communication interfaces, thereby reducing device complexity while maintaining electrical insulation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures sufficient electrical insulation and withstand voltage between the low-voltage and high-voltage system circuits, preventing electrical hazards and reducing costs associated with dual microcontroller implementation.
Implementation Method 1
a water temperature sensor that is included in a low-voltage system circuit and outputs a voltage signal according to a temperature of hot water
Implementation Method 2
a V/f conversion unit for water temperature detection that is included in the low-voltage system circuit and converts the voltage signal output from the water temperature sensor into a frequency signal
Implementation Method 3
a digital isolator for water temperature detection that transmits the frequency signal to the microcontroller while maintaining electrical insulation between the V/f conversion unit for water temperature detection and the microcontroller
Implementation Method 4
a heater element that is included in a high-voltage system circuit and generates heat by power supplied from a high-voltage battery
Data Source
AI summary
This vehicle-mounted air conditioner control device (1) comprises: a PTC heater (H) that is included in a high-voltage system circuit (HV) and generates heat by the power supplied from a high-voltage battery (B2); and a microcomputer (10) that is included in the high-voltage system circuit (HV) and controls the power supply from the high-voltage battery (B2) to the PTC heater (H). This vehicle-mounted air conditioner control device (1) further comprises: a water temperature sensor (151, 152) that is included in a low-voltage system circuit (LV) and outputs a voltage signal corresponding to the temperature of hot water; and a V/f conversion unit (161, 162) that is included in the low-voltage system circuit (LV) and converts the voltage signal output from the water temperature sensor (151, 152) into a frequency signal. This vehicle-mounted air conditioner control device (1) further comprises a digital isolator (171, 172) that transmits the frequency signal to the microcomputer (10) while maintaining electrical insulation between the V/f conversion unit (161, 162) and the microcomputer (10).