Voltage Transformer Circuit for Spark Plug Ionic Current Measurement
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Solution Overview
Problem
Existing ignition systems with switch-on spark suppression diodes hinder ionic current measurement due to high electrical resistance in combustion chamber contents, requiring higher voltages than vehicle system voltage, and alternative methods to generate higher voltages for measurement are complex and not widely adopted.
Innovation Solution
A voltage transformer circuit with a capacitor loop connected in series on the secondary side, allowing charging and discharging currents to flow in the same direction through a switch-on spark suppression diode, enabling ionic current measurement without premature capacitor discharge, using diodes or switches to control current paths and a secondary capacitor for enhanced measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a switch-on spark suppression diode is used to prevent premature ignition, then reliability is improved, but ionic current measurement capability deteriorates because the diode blocks the discharge current
Solution Approach 1:
The circuit is divided into two separate branches: a first branch for charging the capacitor and a second branch for discharging the capacitor. Each branch has its own diode that allows current flow in only one direction. This segmentation enables the charging current and discharging current to flow through different paths while both passing through the switch-on spark suppression diode in the same direction, thus allowing ionic current measurement without causing premature ignition.
2Device complexity
If vehicle system voltage is used for ionic current measurement, then device complexity is reduced, but measurement capability deteriorates due to high electrical resistance requiring higher voltage
Solution Approach 1:
The system uses periodic charging and discharging of the capacitor. During the charging phase, the capacitor is charged through the first branch from the vehicle system voltage. During the discharging phase, the capacitor discharges through the second branch, providing the higher voltage needed for ionic current measurement. This periodic action allows the system to achieve the required measurement voltage without permanently increasing system complexity.
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 cost-effective combination of switch-on spark suppression diodes with ionic current measurement by ensuring both charging and discharging currents can pass through the diode, allowing for accurate ionic current measurement with reduced outlay, using a resistor in the secondary branch for voltage drop measurement.
Implementation Method 1
the vehicle system voltage of a vehicle by means of a transformer. When the primary voltage is applied to the transformer, a strong magnetic field change immediately occurs on the secondary side thereof, so that a voltage is induced in the electrodes of the spark plug
Implementation Method 2
the secondary voltage generated by a transformer of the voltage transformer circuit is used for charging a capacitor, which is arranged in a loop... After the arc discharge is extinguished, the capacitor is discharged by means of an ionic current
Implementation Method 3
modern ignition systems are often equipped with a switch-on spark suppression diode, which is arranged between the spark plug and the transformer. The switch-on spark suppression diode blocks a secondary current, which is caused by switching on the ignition system
Data Source
AI summary
A voltage transformer circuit is described for supplying a spark plug with ignition energy and for ionic current measurement. A transformer of the circuit generates a secondary voltage from a primary voltage and applies the secondary voltage to the spark plug to ignite an electric arc. Using a current effected by the secondary voltage, a capacitor is charged to a breakdown voltage of a Zener diode bridging the same, via a first branch, which leads from the transformer to a first of two sides of the capacitor. The primary voltage is disconnected from the transformer in order to extinguish the electric arc. The capacitor delivers charges for an ionic current via a second branch, which connects the second side of the capacitor to the transformer. A measuring signal of the ionic current is obtained by measuring a voltage drop at a measuring resistor.