Vehicle Igniter Circuit for Stable Ignition Confirmation
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Solution Overview
Problem
Conventional igniters for vehicle engines face malfunctions due to defects in the joint or bonding portion between wires and pads, leading to incorrect ignition confirmation signals, and are susceptible to noise disturbances that affect the reliability of the ignition confirmation process.
Innovation Solution
The igniter design includes a switch element with input, output, and control electrodes, a current detection resistor formed by a bonding wire, and a control IC that generates an ignition confirmation signal based on the voltage of a third lead, with capacitors connected between the detection and reference voltage input terminals of comparators to suppress noise and maintain accurate voltage comparisons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wire is used as a current detection resistor in the igniter, then the igniter can detect ignition status, but the joint or bonding portion between the wire and pad may deteriorate due to thermal expansion and contraction, causing resistance value changes and malfunction
Solution Approach 1:
The patent changes the physical state of the current detection resistor from a wire form to a film form deposited directly on the semiconductor substrate. This parameter change eliminates the bonding joints between wire and pad, preventing deterioration from thermal cycling. The film resistor maintains stable resistance values while withstanding temperature variations during engine operation.
Solution Approach 2:
The patent replaces the mechanical wire-bonding system with a deposited film system. Instead of using physical wires that require bonding joints to the pad, the current detection resistor is formed as a thin film directly on the semiconductor substrate, eliminating the mechanical bonding interface that is susceptible to thermal fatigue and resistance changes.
2Measurement precision
If noise is superimposed on the circuitry of the igniter, then the impedance difference between signal paths causes phase differences in noise, but this disturbs the output of the ignition confirmation signal
Solution Approach 1:
The patent applies equipotentiality by connecting the negative terminals of both comparators to a common ground potential. This ensures that noise affecting both comparison circuits experiences the same potential reference, eliminating phase differences caused by unequal impedance paths. The common ground creates equipotential conditions that prevent noise-induced voltage mismatches between the two comparator inputs.
Data Source
AI summary
An igniter includes a switch element with input, output control electrodes, a first lead in contact with the input electrode and connected to a primary coil of an ignition coil, a second lead that is grounded, a third lead spaced apart from the first and second leads, a first bonding wire connecting the output electrode and the third lead, a second bonding wire connecting the third lead and the second lead, and a control IC that drives the switch element based on an ignition instruction signal from an engine control unit. The control IC generates an ignition confirmation signal based on the voltage of the third lead, and outputs the signal to the engine control unit.