Passive Infrared Sensing Circuit Startup With Capacitor Pre-Charging
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Solution Overview
Problem
Occupancy and vacancy sensors often require manual intervention to turn on lighting loads, and existing wall-mounted load control devices with pyroelectric detectors face delays in becoming functional due to inefficient capacitor charging methods, leading to prolonged startup times.
Innovation Solution
A passive infrared sensing circuit with a pyroelectric detector, operational amplifiers, and diodes is used to charge capacitors efficiently, allowing the system to quickly transition from a charging state to an operational state, enabling rapid detection of occupancy and vacancy conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional capacitor charging methods are used in pyroelectric detector circuits, then the circuit can eventually become operational, but the startup time is prolonged (several minutes)
Solution Approach 1:
The patent applies preliminary action by pre-charging capacitors to appropriate voltage levels before the pyroelectric detector circuit needs to become operational. The control circuit proactively manages the charging state of capacitors in the sensing circuit, ensuring they are ready to immediately process signals when needed, rather than waiting for natural charging during operation.
Solution Approach 2:
The patent introduces a control circuit as an intermediary between the power source and the pyroelectric detector circuit. This control circuit actively manages the charging state of capacitors, providing controlled current paths and voltage regulation to accelerate the charging process. The intermediary control circuit coordinates the charging of multiple capacitors to achieve rapid startup while maintaining proper voltage levels for detector operation.
2Use of energy by moving object
If manual intervention is required to turn on lighting loads, then energy consumption can be reduced, but user convenience deteriorates
Solution Approach 1:
The patent implements self-service through occupancy sensors that automatically detect the presence or absence of occupants and control lighting loads without manual intervention. The system monitors environmental conditions (occupancy status) and autonomously makes control decisions, eliminating the need for users to manually switch lights on or off while maintaining energy efficiency through automatic load management.
Solution Approach 2:
The patent employs feedback mechanisms where occupancy sensors continuously monitor the space for the presence or absence of occupants and provide this information to the control circuit. The control circuit processes this feedback and automatically adjusts the lighting load state accordingly, creating a closed-loop system that responds to environmental conditions and optimizes energy consumption based on actual occupancy patterns.
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 enables rapid startup and functional readiness of the load control device, reducing startup time from several minutes to approximately 18 seconds, allowing for immediate detection of occupancy and vacancy conditions.
Implementation Method 1
a pyroelectric detector configured to receive infrared energy and generate an output signal in response to the received infrared energy
Implementation Method 2
a first amplifier circuit configured to amplify the output signal of the pyroelectric detector to generate an amplified signal
Implementation Method 3
a diode having an anode coupled to the output of the operational amplifier and a cathode coupled to the inverting input of the operational amplifier. Prior to the passive infrared sensing circuit entering an operational state, the operational amplifier is configured to drive a voltage at the output high towards the supply voltage and the diode is configured to conduct at least a portion of a charging current from the supply voltage to charge the first capacitor
Data Source
AI summary
A control device may comprise a passive infrared sensing circuit configured to operate in a charging state to charge one or more capacitors to appropriate voltages for operation in an operational state of the sensing circuit. The sensing circuit may comprise a pyroelectric detector configured to generate an output signal in response to received infrared energy, and first and second amplifier circuits configured to amplify the output signal. The control device may comprise a control circuit coupled to receive a sensing signal from the second amplifier circuit. Prior to the operational state, a capacitor of the first amplifier circuit may charge through a diode coupled between an output and an inverting input of an operational amplifier. In addition, prior to the operational state, a capacitor of the passive infrared sensing circuit may charge through the control circuit until the magnitude of a voltage across the capacitor exceeds a threshold voltage.