Capacitive Input Circuit Layout to Isolate LED Switching Noise
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Solution Overview
Problem
The detection capacitance of an electrostatic sensor in input devices is influenced by the light emission state of a light-emitting diode (LED), leading to variations in capacitance that affect the device's performance.
Innovation Solution
An input device is designed with a light-emitting diode (LED), a switching element to control the LED's state, an electrostatic sensor with a detection electrode capacitively coupled to a circuit portion between the LED and the switching element, and a capacitor connected to the circuit portion and a fixed potential point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light-emitting diode is used in the input device, then illumination or indication function is provided, but the detection capacitance of the electrostatic sensor varies depending on the LED's light emission state
Solution Approach 1:
A capacitor is introduced as an intermediary component between the LED circuit portion and the electrostatic sensor. This capacitor acts as a buffer that decouples the electrical influence of the LED's switching state from the sensor's detection circuit, thereby maintaining consistent detection capacitance while preserving the LED's illumination function
Solution Approach 2:
The capacitor is positioned to electrically separate the LED circuit portion from the electrostatic sensor. By extracting the LED's electrical influence from the sensor's detection path through this intermediate component, the sensor's measurement precision is maintained independent of the LED's operational state
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 suppresses the influence of the LED's light emission state on the detection capacitance of the electrostatic sensor, ensuring consistent performance regardless of the LED's state.
Implementation Method 1
an electrostatic sensor having a detection electrode capacitively coupled to a circuit portion disposed between the light-emitting diode and the switching element
Implementation Method 2
a capacitor having a first terminal connected to the circuit portion and a second terminal connected to a fixed potential point
Data Source
AI summary
An input device includes: a light-emitting diode; a switching element connected in series with the light-emitting diode, the switching element switching the light-emitting diode between the on and off states; an electrostatic sensor having a detection electrode capacitively coupled to a circuit portion disposed between the light-emitting diode and the switching element; and a capacitor having a first terminal connected to the circuit portion and a second terminal connected to a fixed potential point.