Segmented PTC Heater Startup for Low-Temperature Current Control
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Solution Overview
Problem
PTC heaters in vehicle air conditioners experience high starting currents at low ambient temperatures, leading to protection shutdowns and poor user experience due to repeated activation and deactivation, and existing solutions like boost circuits and current protectors increase costs.
Innovation Solution
A PTC heater with independently controllable modules that can be selectively started based on ambient temperature, allowing partial activation before full activation to reduce starting current and prevent protection shutdowns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all PTC modules are started simultaneously at low ambient temperature, then the heating function is activated, but the starting current exceeds protection limits causing shutdown
Solution Approach 1:
The PTC heater is divided into multiple independently controllable modules. Instead of starting all modules simultaneously, the control method segments the startup process by first activating only one module to preheat it, then gradually activating remaining modules. This segmentation reduces the instantaneous starting current to below protection thresholds while still achieving full heating capacity.
Solution Approach 2:
The control method performs preliminary action by preheating one PTC module before activating others. The first module is started and allowed to heat up for a predetermined time, increasing its resistance and reducing overall starting current demand. This preliminary heating action prevents excessive current from triggering protection shutdown.
2Reliability
If a PTC current protector is used to limit current, then protection is provided, but the heater is repeatedly deactivated and activated causing poor user experience
Solution Approach 1:
The system performs preliminary action by proactively segmenting the startup sequence before current protection would be triggered. By preheating one module first and then gradually activating others, the control method prevents current exceedance entirely, eliminating the need for repeated activation/deactivation cycles that occur with traditional protectors.
Solution Approach 2:
The control method incorporates feedback by monitoring ambient temperature and system state to dynamically adjust the startup sequence. Based on feedback from temperature sensors and module status, the controller determines the optimal activation sequence, ensuring current remains within safe limits while maintaining continuous heating operation.
3Object-affected harmful factors
If boost circuits are introduced to reduce starting current, then current is reduced, but electrical control costs significantly increase
Solution Approach 1:
The PTC modules serve themselves through inherent positive temperature coefficient characteristics. As each module operates, its resistance automatically increases, naturally limiting current without external boost circuits. The system uses its own thermal and electrical properties to regulate current, eliminating the need for complex external current-reducing circuitry.
Solution Approach 2:
The control method exploits parameter changes in the PTC modules themselves - specifically the resistance increase with temperature. By controlling the activation sequence and timing, the system leverages the natural resistance change of PTC materials to reduce starting current, avoiding the need for additional electrical components like boost circuits.
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
Reduces starting current and ensures normal activation of the PTC heater with a simple and cost-effective structure, providing a better user experience by avoiding excessive current during cold starts.
Implementation Method 1
a first PTC module (11) is started and then operated for a period of time to preheat the first PTC module (11), and then both the first PTC module (11) and the second PTC module (12) are started to start both the first PTC module (11) and the second PTC module (12) simultaneously to activate the entire PTC heater (1). The temperature of the started PTC module itself will also increase with operation (its resistance value increases) so that the current gradually decreases
Data Source
AI summary
A positive temperature coefficient (PTC) heater for use in a vehicle air conditioner. The PTC heater comprises a plurality of independently electrically controllable PTC modules that can be selected. All the PTC modules are directly started simultaneously to activate the entire PTC heater; or the operation of one or some of the PTC modules is started before all the PTC modules are started simultaneously to activate the entire PTC heater. In addition, a method for controlling the PTC heater and a control system for operating the control method are also provided. By controlling the coordinated operation of the PTC heater and a compressor, the purposes of reducing power consumption to increase energy efficiency and extending the range of an electric bus are achieved.