Auxiliary Microcontroller Circuit for High-Voltage Discharge
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Solution Overview
Problem
Existing circuit arrangements for discharging high-voltage energy stores in motor vehicles face challenges in ensuring an accident-proof voltage supply, as they require high-voltage-resistant components and complex insulation due to reliance on the 12-volt vehicle battery, which can be interrupted in accidents.
Innovation Solution
A circuit arrangement using an auxiliary microcontroller operable at low voltage (3-5 volts) with a buffer capacitor, allowing the discharge circuit to function independently of the 12-volt vehicle battery, utilizing a discharge resistor and transistor or DC-to-DC converter for safe discharging, and incorporating monitoring and decoupling mechanisms for safety and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the discharge circuit is supplied from the 12-volt vehicle battery, then the voltage supply is reliable during normal operation, but the supply is interrupted in accident scenarios and complex insulation requirements arise
Solution Approach 1:
The voltage supply system is segmented into two independent parts: a buffer capacitor for accident-mode operation and the vehicle battery for normal operation. This segmentation allows the discharge circuit to operate from different sources depending on the situation, eliminating the need for complex insulation between high-voltage and low-voltage systems while maintaining reliability in both normal and accident scenarios.
Solution Approach 2:
The buffer capacitor is pre-charged to the required voltage level before an accident occurs. This preliminary action ensures that when an accident interrupts the vehicle battery supply, the discharge circuit immediately has sufficient energy to discharge the DC-link capacitor within the required 5 seconds, without needing complex insulation or high-voltage components.
2Reliability
If high-voltage-resistant components are used in the discharge circuit, then the circuit can operate directly from high voltage, but the cost increases and insulation requirements become complex
Solution Approach 1:
A low-voltage intermediary system consisting of a buffer capacitor and low-voltage microcontroller is introduced between the high-voltage DC-link capacitor and the discharge circuit. This intermediary allows the discharge circuit to operate using only low-voltage components, eliminating the need for expensive high-voltage-resistant components while maintaining reliable discharge operation through the buffer capacitor's energy supply.
3Duration of action of moving object
If a large buffer capacitor is used to ensure 5 seconds operation, then the discharge time requirement is met, but the size and cost of the buffer capacitor increases
Solution Approach 1:
The voltage level of the buffer capacitor is increased to 10-15 volts (compared to the 3-5 volts of the microcontroller), which significantly reduces the required capacitance for storing the same amount of energy. This parameter change allows the buffer capacitor to provide sufficient energy for 5 seconds of discharge operation while minimizing its size and cost.
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
Enables safe and efficient discharging of high-voltage energy stores within 5 seconds, even in accident scenarios, without the need for high-voltage-resistant components, ensuring safety and reducing costs by maintaining operation through a low-voltage supply.
Implementation Method 1
which first voltage supply circuit is fed from a buffer capacitor with a voltage of 10-15 volts
Implementation Method 2
the electrical energy stored in the energy store is converted into heat energy only by means of a discharge resistor
Data Source
AI summary
A circuit arrangement discharges at least one energy store charged to a high voltage in a motor vehicle. The circuit arrangement includes a discharge circuit which is connected in parallel with the energy store and contains an auxiliary microcontroller for actuating the discharge circuit. The auxiliary microcontroller can be operated with a low voltage of 3-5 volts and contains a first voltage supply circuit for supplying the auxiliary microcontroller with the low voltage of 3-5 volts, which first voltage supply circuit is fed from a buffer capacitor with a voltage of 10-15 volts. The circuit arrangement further contains a main microcontroller, which is configured to actuate the auxiliary microcontroller so that the latter actuates the discharge circuit.