Ignition Wake-Up Circuit With Hysteresis for Ripple Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing low-cost ignition wake-up circuits for MCUs in vehicles malfunction due to ignition voltage ripple near threshold voltages, causing instability in wake-up operations.
Innovation Solution
An ignition wake-up circuit with a voltage sensing unit that uses hysteresis by setting first and second reference voltages to stabilize wake-up operations, incorporating a voltage detector IC, clamping unit, and resistors to manage ignition voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a low-cost MCU without ignition wake-up function is used, then price competitiveness is improved, but a separate circuit configuration is required which increases device complexity
Solution Approach 1:
The patent combines multiple functions (ignition wake-up detection, voltage sensing, hysteresis control, and clamping) into a single integrated circuit configuration. The voltage sensing unit integrates the wake-up detection logic with reference voltage comparison, eliminating the need for separate wake-up circuitry and reducing overall system complexity while maintaining low-cost MCU usage.
Solution Approach 2:
The voltage sensing unit serves multiple functions simultaneously: it detects ignition wake-up events, provides hysteresis-based stable switching, clamps voltage to protect the MCU, and generates wake-up signals. This multi-functional design reduces the number of separate components needed, thereby reducing device complexity while maintaining price competitiveness.
2Device complexity
If a simple ignition wake-up circuit is used, then device complexity is reduced, but voltage ripple near threshold causes malfunction and reduces reliability
Solution Approach 1:
The circuit establishes reference voltages (first reference voltage higher than second reference voltage) before ignition voltage arrives. The voltage sensing unit is pre-configured with these reference levels, enabling it to immediately and reliably detect when ignition voltage exceeds the threshold without being affected by ripple, thus ensuring stable wake-up operation.
Solution Approach 2:
The hysteresis mechanism provides feedback-based stability: when ignition voltage exceeds the first reference voltage, the wake-up signal is activated; when it falls below the second reference voltage, the signal deactivates. This feedback loop prevents oscillation near the threshold and eliminates ripple-induced malfunctions, ensuring reliable operation.
3Reliability
If hysteresis with first and second reference voltages is implemented, then wake-up operation stability is improved, but device complexity increases
Solution Approach 1:
The patent merges the hysteresis comparison logic with the voltage sensing functionality into a single integrated unit. Rather than adding separate hysteresis circuitry to an existing simple wake-up circuit, the design integrates both functions in one block, minimizing the increase in device complexity while achieving stable wake-up operation.
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
Stabilizes ignition wake-up operations by managing voltage ripples, reducing part count, and enhancing price competitiveness through optimized circuit design.
Implementation Method 1
a voltage sensing unit outputting a wake-up signal according to the magnitude of the ignition voltage, wherein the voltage sensing unit outputs the wake-up signal when the ignition voltage reaches a voltage level greater than or equal to a first reference voltage
Implementation Method 2
the clamping unit can clamp the ignition voltage to a first voltage or lower... the clamping unit may include a Zener diode
Implementation Method 3
the voltage sensing unit outputs the wake-up signal when the ignition voltage reaches a voltage level greater than or equal to a first reference voltage from a voltage less than the first reference voltage, and outputs a low signal when the ignition voltage reaches a voltage level less than or equal to a second reference voltage from a voltage greater than or equal to the second reference voltage
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
An ignition wake-up circuit, according to an embodiment of the present invention, comprises: an input node receiving an ignition voltage as an input; an output node outputting a wake-up voltage; and a voltage sensing unit outputting a wake-up signal according to the magnitude of the ignition voltage. The voltage sensing unit outputs the wake-up signal when the ignition voltage reaches a voltage level greater than or equal to a first reference voltage from a voltage less than the first reference voltage, and outputs a low signal when the ignition voltage reaches a voltage level less than or equal to a first reference voltage from a voltage less than the first reference voltage, and output a low signal when the ignition voltage reaches a voltage less than or equal to a second reference voltage from a voltage greater than the second reference voltage, and the first reference voltage is greater than the second reference voltage.