PIR Sensing Circuit With Stable Biasing to Reduce False Triggers
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Solution Overview
Problem
Consumer electronic devices face issues with false triggering due to noise sensitivity in passive infrared (PIR) sensors, leading to unnecessary power consumption and disturbances in low-power standby modes.
Innovation Solution
A low power sensing circuit using a pyroelectric sensor with an integrated microcontroller that provides a stable power supply through an internal operational amplifier, reducing noise and eliminating the need for additional power components, thereby minimizing false triggers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PIR sensor is used to detect user presence, then the device can wake from standby mode, but the sensor's noise sensitivity causes false triggers and unnecessary power consumption
Solution Approach 1:
The patent combines the PIR sensor, operational amplifier, and power supply circuit into an integrated low-power sensing module. The sensor is directly connected to the microcontroller's internal operational amplifier, which provides both signal amplification and power supply, eliminating the need for separate power components and reducing overall system power consumption while maintaining reliable detection
Solution Approach 2:
The operational amplifier acts as an intermediary between the PIR sensor and the microcontroller. It amplifies the weak sensor signal and provides a stable power supply to the sensor, thereby reducing noise sensitivity and preventing false triggers while enabling reliable user presence detection at low power levels
2Reliability
If additional power supply components are added to the PIR sensor, then noise and false triggering are reduced, but device complexity and cost increase
Solution Approach 1:
The microcontroller's internal operational amplifier is designed to serve multiple functions: it amplifies the PIR sensor signal, provides a stable power supply to the sensor, and reduces noise. This multi-functional approach eliminates the need for separate power supply components, reducing device complexity and cost while maintaining sensor stability
Solution Approach 2:
The sensing circuit is designed to be self-sufficient by using the microcontroller's internal resources. The operational amplifier within the microcontroller automatically provides power and signal conditioning to the PIR sensor without requiring external components, thereby simplifying the overall circuit design and reducing the number of parts needed
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 false triggering and power consumption by providing a stable power supply to the PIR sensor, ensuring reliable detection of user presence and efficient operation of consumer electronic devices.
Implementation Method 1
The low power sensor may be a PIR sensor, such as a pyroelectric sensor
Data Source
AI summary
A consumer electronic device includes a low power. e.g. pyroelectric, sensor (8) arranged to detect the presence of a person (6), to switch from standby to full power mode. The sensor (8) may output a small analogue signal which is input to a microcontroller (7) for amplification and digital conversion. The microcontroller (7) is configured to supply power to the sensor (8), for example by configuring an integrated reference voltage source as an input to an integrated operational amplifier which is used to supply power to the sensor. This provides a stable low power supply, thereby reducing noise and false triggering of the sensor. Also, there may be no need to provide an additional power supply for the sensor, so reducing the number of components required and allowing for a low-cost and compact sensing circuit (5).