Ignition Coil Power Semiconductor Gate Control With Single Capacitor
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Solution Overview
Problem
The existing power semiconductor devices for ignition systems face challenges in downsizing due to the need for separate circuits for over-energization cutting-off and gradual cutting-off functions, and the use of gate capacitance results in limited controllability of cutting-off time, requiring additional capacitors which complicates design and increases size.
Innovation Solution
A power semiconductor device with a control circuit that includes a first constant current source, a first transistor, a resistor, a capacitor, and a second transistor, allowing for integrated over-energization and gradual cutting-off functions using a single capacitor, enabling precise control of cutting-off time and downsizing the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate circuits are provided for over-energization cutting-off function and gradual cutting-off function, then the reliability of protection functions is improved, but the device size increases and circuit complexity increases
Solution Approach 1:
The patent merges the over-energization cutting-off function and gradual cutting-off function into a single integrated circuit. The control circuit includes a constant current source that charges a capacitor during switching element operation. When the capacitor voltage reaches a reference level, a comparator triggers both the over-energization cutting-off and initiates gradual discharge through a discharge transistor, eliminating the need for separate circuits while maintaining both protection functions.
Solution Approach 2:
The control circuit is designed to perform multiple functions using shared components. The capacitor serves dual purposes: monitoring for over-energization conditions and providing the charge reservoir for gradual discharge control. The same constant current source charges the capacitor for over-energization detection and the discharge transistor controls gradual discharge, making each component multi-functional rather than dedicated to a single function.
2Device complexity
If gate capacitance of switching element is used for cutting-off timing control, then the number of external capacitors is reduced, but the controllability of cutting-off time deteriorates because the small capacitance makes it difficult to extend cutting-off time beyond several milliseconds
Solution Approach 1:
The patent changes the controlling parameter from relying solely on the fixed gate capacitance value to using a controllable discharge process. By introducing a discharge transistor that can be controlled to discharge the capacitor at a regulated rate, the cutting-off time becomes adjustable through the discharge control circuit rather than being fixed by the small gate capacitance value. This allows cutting-off times to be extended beyond the natural discharge time of the gate capacitance alone.
3Manufacturing precision
If one capacitor is provided for each cutting-off function (over-energization and gradual cutting-off), then the design precision of each function is improved, but the device size increases and downsizing is obstructed
Solution Approach 1:
The patent combines the capacitive elements for both functions into a single capacitor. The same capacitor that detects over-energization conditions also serves as the charge reservoir for the gradual discharge function. This merging eliminates the need for two separate capacitors while maintaining the precision of both functions through careful circuit design, including using a comparator for precise voltage detection and a controlled discharge transistor for precise discharge timing.
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 ensures downsizing of the power semiconductor device by integrating the over-energization and gradual cutting-off functions, improving controllability of cutting-off time and reducing the number of required capacitors, thus enhancing design flexibility and reducing costs.
Implementation Method 1
a capacitor with one end thereof connected to the control terminal of the first transistor and an other end thereof grounded
Implementation Method 2
The power semiconductor device according to claim 1, wherein the control circuit includes a first constant current source
Data Source
AI summary
The object of the present disclosure is to provide a power semiconductor device capable of miniaturization. According to the present disclosure power semiconductor device includes a semiconductor switching element configured to control a current flowing through a primary coil composing an ignition coil, and a control circuit configured to control drive of the semiconductor switching element, in which the control circuit includes a first constant current source, a first transistor with an output terminal thereof connected to a control terminal of the semiconductor switching element, a resistor with one end thereof connected to a control terminal of the first transistor and an other end thereof connected to the constant current source, a capacitor with one end thereof connected to the control terminal of the first transistor and an other end thereof grounded, and a second transistor with an input terminal thereof connected to the resistor and an output terminal grounded.