Adjustable Pulse Width Circuit for Diesel Reductant Injectors
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Solution Overview
Problem
Existing control systems for automotive exhaust after-treatment do not allow easy adjustment of the pulse width of the trigger pulse delivered to an injector driver, necessitating a solution that allows for increased pulse width without altering the voltage or frequency.
Innovation Solution
A pulse width generator circuit utilizing first and second comparator circuits, D flip-flops, and a current mirror to extend the output pulse width beyond the input pulse width, using a fixed voltage input trigger pulse, without changing the voltage or frequency, by employing a current mirror for constant charging and capacitor charging to reset the flip-flops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the pulse width of the trigger pulse is increased to control flow rate, then the flow rate control flexibility is improved, but the voltage or frequency of the trigger pulse must be changed which is undesirable
Solution Approach 1:
The circuit segments the pulse width control function from the trigger pulse parameters (voltage and frequency). By using a dedicated pulse width generator circuit with adjustable timing components, the pulse width can be independently controlled without affecting voltage or frequency, thus resolving the contradiction between flow rate control flexibility and ease of operation.
Solution Approach 2:
The patent introduces an intermediary pulse width generator circuit between the trigger pulse source and the injector driver. This intermediary circuit allows adjustment of pulse width through timing components while maintaining the original trigger pulse voltage and frequency, enabling flexible flow rate control without direct modification of trigger pulse parameters.
2Device complexity
If existing control systems are used, then the system simplicity is maintained, but the pulse width adjustment capability is limited
Solution Approach 1:
The pulse width generator circuit is designed with universal applicability to various injector types and control systems. By implementing a standardized circuit architecture that can be integrated into different automotive exhaust after-treatment systems, the patent achieves enhanced pulse width adjustment capability while maintaining relative system simplicity through modular design.
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 adjustable output pulse width from 0.25 to 30 milliseconds, allowing for controlled flow rate of the injector at a given frequency and voltage, eliminating the need for an op-amp integrator and providing flexibility in exhaust after-treatment systems.
Implementation Method 1
The current mirror is connected to the output of the second flip-flop to provide a constant charging current for the capacitor
Implementation Method 2
as soon as the capacitor charges, a reset of the second flip-flop is activated and the output of the second flip-flop goes to zero
Data Source
AI summary
A method adjusts a pulse width of a signal. The method provides a fixed voltage input trigger pulse (34), of a certain pulse width, to a pulse width generator circuit (10) and provides an output pulse (52) from the pulse width generator circuit such that a pulse width of the output pulse is longer than the certain pulse width, without changing a voltage or frequency of the input trigger pulse. The method is used to drive an injector of a diesel reductant delivery system to inject fluid into an exhaust flow path.