Ignition IGBT Control Circuit With Zener Noise Filtering
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Solution Overview
Problem
Integrated circuits used in ignition systems for internal combustion engines often malfunction due to noise superimposed on the gate electrode voltage, leading to inappropriate on and off switching of insulated gate bipolar transistors (IGBTs).
Innovation Solution
An integrated circuit design that includes a Zener diode with a specific capacitance value, coupled between the gate and emitter electrodes, filters out noise by clamping input voltages within a predetermined range, ensuring the IGBT is controlled based on the intended drive signal, irrespective of superimposed noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the control circuit operates directly from the gate electrode voltage line, then the circuit can be simplified and operate with minimal components, but noise superimposed on the voltage line causes malfunction and unreliable transistor switching
Solution Approach 1:
A Zener diode is introduced as an intermediary component between the gate electrode voltage line and the control circuit. The Zener diode clamps the voltage to a predetermined range, filtering out noise while allowing the control circuit to operate reliably. This mediator protects the control circuit from voltage fluctuations without requiring a completely separate power supply system.
Solution Approach 2:
The patent changes the voltage parameter characteristics by using a Zener diode to clamp the gate electrode voltage within a specific range. This parameter control ensures that even when noise is superimposed on the voltage line, the control circuit receives a stabilized voltage signal, preventing malfunction while maintaining circuit simplicity.
2Reliability
If noise filtering components are added to the gate electrode voltage line, then transistor switching reliability improves, but device complexity and component count increase
Solution Approach 1:
The Zener diode serves as a compact intermediary filtering component that can be easily integrated into the existing circuit layout. It provides effective noise filtering and voltage clamping in a single component, avoiding the need for complex RC filters or multiple protection components that would increase device complexity.
Solution Approach 2:
The patent uses a simple, inexpensive Zener diode for noise filtering rather than complex active filtering circuits. This passive component approach provides reliable noise suppression with minimal cost and complexity addition, treating the filtering function as a basic protective measure rather than a complex signal processing requirement.
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 reduces noise interference, ensuring reliable on and off switching of the IGBT, thereby preventing malfunctions and maintaining proper ignition system operation even under noisy conditions.
Implementation Method 1
a Zener diode having such a capacitance that, responsive to the first signal and the second signal being both inputted to the first line, the control circuit controls the on and off of the transistor in response to the first signal irrespective of the second signal
Data Source
AI summary
An integrated circuit for controlling an ignition system including a coil. The integrated circuit includes a transistor configured to control a current flowing through the coil, a first line coupled to a control electrode of the transistor, a second line coupled to an electrode of the transistor on the ground side thereof, a control circuit configured to control on and off of the transistor based on a voltage level of the first line, and a Zener diode having a cathode coupled to the first line and an anode coupled to the second line. The Zener diode has such a capacitance that, when a first signal, and a second signal of a higher frequency, are inputted to the first line, the control circuit controls the on and off of the transistor in response to the first signal irrespective of the second signal.