Photodetector Bias Switching for Fast Low-Power Stabilization
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Solution Overview
Problem
Wearable health monitoring devices face challenges in quickly stabilizing the output voltage of photoreceiver circuits, leading to prolonged power consumption due to the Miller effect and slow stabilization times in phototransistor circuits, which delays the readiness of other components like amplifiers and microcontrollers.
Innovation Solution
The introduction of an external bias resistor controlled by a microcontroller to parallel with the main resistor in photodetector circuits, allowing for rapid bias setting and subsequent disconnection to minimize stabilization time, enabling faster wake-up and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the photodetector circuit uses a main resistor to bias the phototransistor, then the circuit provides stable operation, but the stabilization time is prolonged due to the Miller effect and capacitor charging time
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor connected to the photodetector circuit before the actual measurement phase. A bias resistor is used to charge the capacitor during a precharge period, so that when the measurement phase begins, the capacitor is already charged and the circuit stabilizes quickly without waiting for slow capacitor charging during measurement. This resolves the contradiction by performing the time-consuming stabilization action in advance.
2Use of energy by moving object
If the photodetector circuit is switched on quickly to reduce power consumption, then power savings are achieved, but the output voltage takes time to reach the operational level due to capacitance and Miller effect
Solution Approach 1:
The patent uses preliminary action by pre-charging the capacitor before the measurement phase. The bias resistor charges the capacitor during a precharge interval, so when the photodetector is switched on for measurement, the voltage stabilizes immediately rather than taking time to charge the capacitor during the measurement window. This enables quick switching for power savings while maintaining fast voltage stabilization during actual operation.
Solution Approach 2:
The patent applies dynamics by making the bias resistor configurable - it can be connected during precharge phases and disconnected or adjusted during measurement phases. This dynamic configuration allows the circuit to optimize between power consumption and stabilization speed depending on the operational phase, resolving the contradiction between these two parameters.
3Measurement precision
If other components (amplifier, microcontroller) wait for the photodetector to stabilize, then measurement accuracy is ensured, but power is consumed in vain during the waiting period
Solution Approach 1:
The patent applies preliminary action by pre-charging the capacitor and stabilizing the photodetector output voltage before the measurement phase begins. This ensures that when the amplifier and microcontroller start processing signals, the photodetector is already stable and ready, eliminating the need for these components to wait and consume power during stabilization. Measurement precision is maintained while avoiding wasted energy.
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
This approach significantly reduces the setup time of photodetector circuits by 80-96%, achieving both rapid stabilization and high gain with minimal power usage, essential for wearable devices.
Implementation Method 1
a photodetector sensitive to light
Data Source
AI summary
The present invention introduces an arrangement for enhancing the performance of an electronic circuit comprising a phototransistor (Q). Either a common-collector or a common-emitter connected phototransistor (Q) has a main resistor (RL), and at least one external bias resistors (RL2, RL3, RL4), each in parallel to one another. The microcontroller may directly control the voltage outputs or act via respective switches (S1, S2) regarding each respective resistor. When the electronic circuit with the phototransistor (Q) is switched on, at least one of the external bias resistors (RL2, RL3, RL4) are switched on. The voltage output rise time is short, and when the bias has been set, the external bias resistor(s) are disconnected functionally. This means that during the actual measurement with the electric circuit, only the main resistor (RL) is used in the connection.