Kickback-Limited Soft Shutdown Circuit for Coil Ignition Systems
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Solution Overview
Problem
Existing ignition systems face challenges in preventing unwanted sparks during soft shutdown of a charged coil, which can lead to overheating and damage, while also needing to minimize the time of gradual discharge to avoid prolonged heating.
Innovation Solution
A current-control circuit with a kickback voltage limiter that monitors the collector voltage and adjusts the soft shutdown profile to limit kickback voltage, allowing for flexible shutdown timing without overheating or sparking, by controlling the rate of coil current reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the coil current is gradually reduced during soft shutdown, then kickback voltage is minimized and sparking is prevented, but the shutdown time increases causing prolonged heating
Solution Approach 1:
The patent applies dynamics by making the soft shutdown profile adjustable and adaptive. The controller can modify the shutdown rate dynamically based on system conditions, allowing optimization between minimizing kickback voltage and reducing shutdown time. This is achieved through configurable shutdown profiles that enable the system to adapt the current reduction rate to specific operational requirements.
Solution Approach 2:
The patent utilizes parameter changes by implementing a configurable shutdown rate parameter. By adjusting this parameter, the system can change the characteristics of the soft shutdown process - either reducing the shutdown rate to minimize kickback voltage or increasing it to reduce shutdown time. This parameter adjustment allows the system to optimize performance based on specific operational conditions without requiring hardware changes.
2Loss of time
If the shutdown rate is increased to reduce shutdown time, then heating is reduced, but kickback voltage increases causing sparking
Solution Approach 1:
The patent implements feedback by monitoring the actual shutdown process and adjusting the shutdown rate accordingly. The controller observes system responses during soft shutdown and modifies the current reduction rate to maintain kickback voltage within safe limits while achieving optimal shutdown time. This feedback mechanism ensures that increasing shutdown rate does not inadvertently cause sparking.
Solution Approach 2:
The system dynamically adjusts the shutdown profile based on real-time conditions. Rather than using a fixed shutdown rate, the controller can modify the rate during the shutdown process, allowing the system to achieve faster shutdown when conditions permit while preventing kickback voltage from exceeding thresholds that would cause sparking.
3Device complexity
If a fixed soft shutdown profile is used, then the circuit is simple to implement, but it cannot adapt to different operating conditions leading to either overheating or prolonged heating
Solution Approach 1:
The patent applies dynamics by implementing a configurable and adaptive soft shutdown profile rather than a fixed one. The controller can adjust shutdown parameters based on different operating conditions, enabling the system to adapt to varying requirements while maintaining reasonable circuit complexity through software or firmware control rather than complex hardware 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
Prevents unintended sparks and reduces heating by limiting kickback voltage during soft shutdown, enabling shorter SSD periods and increased flexibility in coil discharge rates, thus protecting components and improving system reliability.
Implementation Method 1
The abrupt change in the coil current creates a large voltage across the primary coil as the primary coil begins to discharge. This large voltage is transformed by a windings-ratio between the primary and secondary coil.
Implementation Method 2
When the switching device is configured to conduct (i.e., is turned ON), the primary coil is charged by a coil current flowing from the voltage source and through the primary coil and the switching device to the ground. After the coil is charged, the switching device may be configured (i.e., turned OFF) to block the coil current.
Data Source
AI summary
A circuit configured to control a switching device to reduce a current in a charged coil is disclosed. The circuit is configured to monitor a kickback voltage generated by the decreasing current in the coil. The circuit is further configured to adjust a rate at which the current is reduced in order to limit the kickback voltage. Limiting the kickback voltage during shutdown can prevent a spark at a spark gap that is inductively coupled to the coil and can allow for greater flexibility in the time taken to shut down the coil without overheating components or generating an unwanted spark. Additional, limiting the kickback voltage during shutdown can allow for a pseudo ramp wave to control the circuit during the shutdown because voltage spikes cause by abrupt changes in the pseudo ramp wave are limited.