Integrating Circuit Dual-Switch Photodiode Initialization
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Solution Overview
Problem
Conventional photodetecting devices face challenges in achieving both low power consumption and high speed due to the trade-off between reducing power consumption and maintaining drive capability in the integrating circuit.
Innovation Solution
The integrating circuit incorporates a second switch between the reference potential input terminal and the capacitive element, allowing for simultaneous discharge of the capacitive element when initializing the output voltage, thereby reducing the time required for initialization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If power consumption of the integrating circuit is reduced, then power consumption decreases, but the drive capability of the amplifier circuit deteriorates, causing the initialization time to increase
Solution Approach 1:
The patent segments the discharge path of the capacitive element into two separate switches: a first switch connected in parallel with the capacitive element, and a second switch connected between the reference potential input terminal and the capacitive element. This segmentation allows independent control of different discharge paths, enabling the circuit to achieve fast initialization (by closing both switches) while maintaining low power consumption (by keeping switches open during normal operation).
Solution Approach 2:
The second switch is closed before the first switch to pre-charge the capacitive element with reference potential, preparing it for rapid discharge. This preliminary action ensures that when the first switch closes, the capacitive element can discharge immediately through the low-impedance path, achieving fast initialization without requiring high continuous power consumption.
2Measurement precision
If the number of photodiodes is increased to improve image quality, then measurement precision improves, but device complexity and power consumption increase
Solution Approach 1:
The integrating circuit with the dual-switch configuration serves multiple functions: it provides fast initialization, low power consumption, and stable reference potential coupling. This universal design can be applied to each pixel's integrating circuit in a photodiode array, allowing the system to scale to multiple photodiodes without proportionally increasing overall circuit complexity or power consumption.
3Measurement precision
If the number of photodiodes is increased to improve image quality, then measurement precision improves, but power consumption increases
Solution Approach 1:
By segmenting the discharge control into two independent switches, the circuit achieves fast initialization without requiring high continuous power. The first switch provides the main discharge path only when needed, while the second switch provides reference potential coupling with minimal power consumption during normal operation, allowing scaling to multiple photodiodes without proportional power increase.
Solution Approach 2:
The circuit operates in periodic cycles: during normal operation, switches remain open minimizing power consumption; during initialization periods, switches close briefly to reset the capacitive element. This periodic action pattern allows the system to maintain low average power consumption even when multiple photodiodes are active, as each integrating circuit only consumes significant power during brief initialization intervals.
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 configuration enables both low power consumption and high-speed operation by quickly discharging the capacitive element, shortening the time to reach the initial output voltage value.
Implementation Method 1
a photodiode which generates an amount of electric charge according to an amount of incident light
Implementation Method 2
a capacitive element provided between the first input terminal and the output terminal of the amplifier circuit
Data Source
AI summary
A photodetecting device 1 includes a photodiode PD and an integrating circuit 10. The integrating circuit 10 includes an amplifier circuit 20, a capacitive element C, a first switch SW1, and a second switch SW2. The second switch SW2 is provided between a reference potential input terminal to which a reference potential Vref is input and a terminal of the capacitive element C on the inverting input terminal side of the amplifier circuit 20, and the second switch is opened or closed according to the level of a second reset signal Reset2, and is capable of applying the reference potential Vref to the terminal of the capacitive element. Thus, an integrating circuit and a photodetecting device capable of achieving both low power consumption and high speed can be realized.