MPPT Circuit Using Dummy Cell for Ultra-Low Power Harvesting
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Solution Overview
Problem
In ultra-low-power applications, such as battery-free solar harvester sensor nodes, implementing Maximum Power Point Tracking (MPPT) circuitry is challenging due to the low power levels, leading to inefficiencies and increased complexity, making it difficult to achieve effective energy harvesting.
Innovation Solution
A three-terminal photovoltaic cell system with a small 'dummy' cell to measure open-circuit voltage, allowing for simplified MPPT functions and reduced power absorption, enabling efficient energy transfer and system miniaturization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MPPT circuitry is implemented in ultra-low-power applications, then power tracking capability is improved, but power absorption increases and system complexity increases
Solution Approach 1:
The system is divided into two separate photovoltaic generators: a first generator for energy production and a second (dummy) generator for voltage measurement. This segmentation allows the measurement function to be performed with minimal power consumption while the main generator focuses on energy production, resolving the contradiction between tracking capability and power absorption.
Solution Approach 2:
A down-scaled replica (dummy cell) of the main photovoltaic system is created to reproduce the voltage behavior without significant power consumption. This copy enables MPPT measurements to be taken with negligible power absorption, allowing power tracking capability while maintaining ultra-low power operation.
2Reliability
If MPPT circuitry is implemented in ultra-low-power applications, then power tracking capability is improved, but device complexity increases
Solution Approach 1:
The driver circuitry serves multiple functions: it controls the energy transfer circuitry for power conversion and simultaneously responds to the voltage signal from the dummy generator to perform MPPT. This multi-functionality reduces the need for separate dedicated MPPT circuitry, thereby reducing overall device complexity while maintaining power tracking capability.
Solution Approach 2:
The voltage measurement function and the power conversion control function are merged into a single integrated approach where the driver circuitry handles both tasks. By combining these functions, the patent reduces the number of separate components and simplifies the overall circuit architecture.
3Measurement precision
If a dummy cell is added for voltage measurement, then MPPT accuracy is improved, but system area increases
Solution Approach 1:
The dummy photovoltaic generator is designed with a down-scaled configuration that reproduces the voltage characteristics of the main system. By changing the scale parameter while maintaining the functional relationship, accurate voltage measurement is achieved with minimal area occupation, resolving the contradiction between measurement precision and system area.
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 reduces current absorption associated with MPPT functions to nanampere levels, enhances energy efficiency, and allows for system flexibility across varying light conditions while maintaining energy performance, making MPPT attractive for ultra-low-power systems.
Implementation Method 1
both generators may comprise photovoltaic generators
Data Source
AI summary
A first generator produces a first signal that is supplied to an energy storage circuit. Energy transfer circuitry coupled to the energy storage circuit transfers energy stored in the energy storage circuit to an output node. A driver circuit coupled to the energy transfer circuitry switches the energy transfer circuitry between a state where energy from the first signal is stored in the energy storage circuit and a state where energy stored in the energy storage circuit section is delivered to the output node. A voltage at the energy storage circuit varies between an upper value and a lower value around a voltage setting point. A second generator, which is a scaled-down replica of the first generator, produces a second signal that is indicative of an open-circuit voltage of the first generator. The driver circuit uses the second signal to set the voltage setting point.