Vehicle Pre-Charging Circuit Using PTC Heater Resistance
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Solution Overview
Problem
The existing on-board vehicle power systems face challenges in efficiently pre-charging capacitive energy accumulators like double layer capacitors, leading to high compensating currents, thermal issues, and limited system availability due to the complexity and cost of direct voltage transformers, as well as the aging of capacitors caused by temperature and polarization voltage.
Innovation Solution
A motor vehicle system that uses an electric consumer with decreasing resistance over a voltage subrange to pre-charge capacitive energy accumulators in parallel with the on-board vehicle electric system, eliminating the need for direct voltage transformers and reducing thermal stress by leveraging existing components like rear windshield heaters with PTC characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a direct voltage transformer is used to pre-charge the double layer capacitor, then the capacitor can be charged to the on-board voltage, but the system complexity and cost increase considerably
Solution Approach 1:
The patent extracts the pre-charging function from the main voltage transformer and implements it separately using a dedicated pre-charging circuit with switchable resistors. This allows the main transformer to be simplified while maintaining the pre-charging capability through a separate, simpler circuit arrangement.
Solution Approach 2:
The patent introduces switchable pre-charging resistors as intermediary elements between the voltage transformer and the double layer capacitor. These resistors act as mediators to limit and control the charging current during the pre-charging phase, protecting the system from excessive currents while enabling gradual capacitor charging.
2Productivity
If a high charging current is used to charge the double layer capacitor quickly, then the function availability increases, but thermal problems and capacitor aging are exacerbated
Solution Approach 1:
The patent employs dynamically switchable resistor configurations that can be adjusted during the charging process. The circuit transitions from high-resistance switching patterns to lower-resistance patterns as the capacitor charges, enabling optimized current profiles that balance charging speed with thermal management throughout the charging cycle.
Solution Approach 2:
The patent uses periodic switching of the pre-charging resistors in a controlled sequence, alternating between different resistor combinations to deliver charging current in controlled pulses. This periodic action prevents continuous high current flow, reducing thermal stress while maintaining acceptable charging speed through repeated charging cycles.
3Reliability
If switchable power resistors are used for pre-charging, then the pre-charging current can be controlled, but the pre-charging period becomes longer
Solution Approach 1:
The patent segments the pre-charging process into multiple phases by using several switchable resistors that can be activated in different combinations. This segmentation allows the charging current to be controlled in steps, with different resistor pairs engaged at different charging stages to optimize both control precision and charging speed.
Solution Approach 2:
The patent designs the pre-charging circuit so that the same set of switchable resistors serves multiple functions: current limiting, charging control, and potentially diagnostic functions. This multi-functionality reduces the need for additional dedicated components, maintaining control capabilities while minimizing the overall pre-charging time through efficient component utilization.
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 approach allows for fast, reliable, and cost-effective pre-charging of energy accumulators with reduced hardware complexity and thermal impact, enhancing system availability and extending the lifespan of capacitors by managing pre-charging currents effectively.
Implementation Method 1
a PTC heater element 220 which is designed in such a way that its electrical resistance increases with increasing temperature, for limiting a pre-charging current which flows during a pre-charging phase of the double layer capacitor 10
Implementation Method 2
capacitive energy accumulators, such as double layer capacitors
Data Source
AI summary
A motor vehicle includes an on-board vehicle electric system, an electric consumer, whose resistance decreases with the decreasing voltage dropping at the consumer, an electric energy accumulator, and a switching arrangement. The switching arrangement is designed and is connected or connectable to the on-board vehicle electric system, the consumer and the energy accumulator such that in a first switching position, the energy accumulator, and in a second switching position, the switching arrangement, is connected in parallel to the on-board vehicle electric system. The energy accumulator in the second switching position is connected in series to the consumer, and the energy accumulator in the first switching position is not connected in series to the consumer.