Digital Isolator for High-Voltage PTC Heater Control
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Solution Overview
Problem
The existing vehicle-mounted air conditioner control devices face challenges in maintaining sufficient electrical insulation between high-voltage and low-voltage system circuits, making it difficult to accurately detect and control the voltage output from the high-voltage battery and current flowing to the PTC heater while preventing degradation of insulation performance.
Innovation Solution
Incorporating a microcontroller in the low-voltage system circuit, a current detection sensor and V/f conversion unit in the high-voltage system circuit, and digital isolators to transmit frequency signals across the circuits, allowing for safe and accurate control of the PTC heater and motor operations while maintaining electrical insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the water temperature sensor is connected to the high-voltage system circuit, then the microcontroller can directly acquire temperature data, but the insulation performance between high-voltage and low-voltage systems deteriorates
Solution Approach 1:
A digital isolator is introduced as an intermediary component between the high-voltage system circuit (where the water temperature sensor is connected) and the low-voltage system circuit (where the microcontroller resides). The isolator includes a high-voltage side circuit that receives the sensor signal and a low-voltage side circuit that transmits the signal to the microcontroller, while maintaining electrical insulation between the two systems. This allows temperature data acquisition without compromising insulation performance.
2Reliability
If the microcontroller is connected to the low-voltage system circuit, then insulation performance is maintained, but the ability to acquire high-voltage parameters (voltage output from high-voltage battery or current flowing to PTC heater) deteriorates
Solution Approach 1:
The digital isolator serves as a mediator that enables the microcontroller in the low-voltage system circuit to acquire high-voltage parameters (voltage output from the high-voltage battery or current flowing to the PTC heater) without direct electrical connection. The isolator's high-voltage side circuit interfaces with high-voltage parameters, converts them to digital signals, and transmits them through the insulation barrier to the low-voltage side circuit, which delivers the data to the microcontroller.
Solution Approach 2:
The patent replaces direct electrical connection (mechanical/electrical coupling) with optical or electromagnetic signal transmission through the digital isolator. This substitution allows information transfer across the insulation barrier without physical electrical contact, enabling the microcontroller to access high-voltage parameters while maintaining insulation integrity.
3Ease of operation
If the microcontroller is disposed on the low-voltage system circuit side, then direct connection to water temperature sensor is possible, but the complexity of acquiring and transmitting high-voltage parameters increases
Solution Approach 1:
The digital isolator is designed with multi-functionality, serving both as an insulation barrier and as a data transmission channel. It handles multiple functions: maintaining insulation between high-voltage and low-voltage systems, acquiring high-voltage parameters (voltage and current), converting analog signals to digital signals, and transmitting data to the microcontroller. This universal design reduces overall system complexity despite the added insulation requirement.
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 withstand voltage between the low-voltage and high-voltage system circuits, enabling effective electrical conduction control and reducing the risk of insulation degradation, thereby enhancing safety and operational efficiency.
Implementation Method 1
a heater element (H) that is included in a high-voltage system circuit and generates heat by power supplied from a high-voltage battery (B2)
Implementation Method 2
a V/f conversion unit for current detection that is included in the high-voltage system circuit and converts the voltage signal output from the current detection sensor into a frequency signal
Implementation Method 3
a digital isolator for current detection that transmits the frequency signal to the microcontroller while maintaining electrical insulation between the V/f conversion unit for current detection and the microcontroller
Data Source
AI summary
This on-board air conditioner control device comprises: a PTC heater which is contained in a high-voltage circuit and generates heat by means of power supplied from a high-voltage battery; a micro-controller which is contained in a low-voltage circuit and controls the power supplied to the PTC heater from the high-voltage battery; a current detection sensor which is contained in the high-voltage circuit and outputs a voltage signal indicating a value for the current flowing through the PTC heater; a V/f conversion unit which is contained in the high-voltage circuit and converts the voltage signal outputted by the current detection sensor to a frequency signal; and a digital isolator which transmits the frequency signal to the micro-controller while preserving electrical insulation between the V/f conversion unit and the micro-controller.