Igniter Circuit With Adjustable Over-Dwell for Coil Overheating
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Solution Overview
Problem
Automotive ignition systems face issues with overheating and damage due to fixed over dwell times that do not account for varying battery voltages, leading to inefficient current shutdown and excessive power dissipation.
Innovation Solution
An igniter circuit with an adjustable over dwell time based on battery voltage, using circuitry that senses switching device signals instead of directly monitoring battery voltage, allowing for smaller and more efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed over dwell time is used in the igniter circuit, then the circuit design is simple, but the system cannot adapt to varying battery voltages leading to overheating and damage
Solution Approach 1:
The patent introduces an intermediary measurement approach by measuring the rise time of coil current instead of directly sensing battery voltage. This indirect measurement method allows the circuit to adapt to voltage variations without requiring complex voltage sensing circuitry, resolving the contradiction between adaptability and circuit complexity
Solution Approach 2:
The patent changes the parameter used for over dwell time determination from a fixed time value to a variable time value based on measured rise time. By making the over dwell time proportional to the measured rise time, the system adapts to different battery voltages while maintaining a relatively simple circuit structure
2Reliability
If the switching device is abruptly open-circuited to terminate current, then the voltage spike generates sufficient spark for ignition, but the abrupt termination causes overheating and damage to the ignition system
Solution Approach 1:
The patent applies dynamic control by adjusting the over dwell time based on measured rise time rather than using a fixed time value. This dynamic adjustment allows the system to optimize the balance between generating sufficient spark voltage and preventing excessive current duration that would cause overheating, thereby improving reliability without sacrificing ignition efficiency
Solution Approach 2:
The patent implements a feedback mechanism by measuring the rise time of coil current and using this measurement to determine the appropriate over dwell time. This closed-loop approach ensures that the current termination timing is optimized based on actual circuit conditions, preventing overheating while maintaining ignition efficiency
3Adaptability or versatility
If battery voltage is directly monitored to adjust over dwell time, then the system can adapt to voltage variations, but the circuit size increases
Solution Approach 1:
The patent uses an intermediary measurement approach by measuring coil current rise time as a proxy for battery voltage conditions. This indirect measurement requires minimal additional circuitry compared to direct voltage monitoring, achieving voltage adaptation capability while keeping the circuit size small
Solution Approach 2:
The patent enables the circuit to self-adjust the over dwell time based on its own operational characteristics (rise time measurement) without requiring external voltage sensing components. This self-service approach achieves adaptability while minimizing additional circuit size
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
The solution effectively manages current shutdown to prevent overheating and damage, reducing power dissipation and circuit size while maintaining ignition reliability.
Implementation Method 1
The abrupt termination of the current can cause a large voltage across the coil, which can be used to generate a spark for ignition
Implementation Method 2
which could cause overheating and/or damage to the ignition system
Data Source
AI summary
An ignition system may include an igniter circuit to control the current in a coil supplied by a battery based on an input signal from an engine control unit. To prevent overheating, the igniter circuit may be configured to shut down the current in the coil when the input signal is held high for an over dwell period. The disclosed igniter circuit is configured with circuitry to automatically adjust the over dwell period used based on a condition of the battery to prevent overheating without prematurely shutting down. The automatic adjustment includes indirectly monitoring the battery condition based on a current or a voltage of a switching device coupled to the coil.