Active Rectifier Circuit Impedance Matching Energy Harvesting
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Solution Overview
Problem
Energy harvesting systems face inefficiencies due to impedance mismatch between transducers and scavenging interfaces, leading to reduced power transfer and inability to harvest energy when signal amplitudes are low, especially with diode-bridge rectifiers that cannot be actively controlled.
Innovation Solution
A rectifier circuit with switches and control logic that actively manages energy transfer by storing and releasing energy in an inductor, optimizing power transfer through adjustable time intervals and threshold currents to match impedance between the transducer and the rectifier circuit, even at low signal amplitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a diode-bridge rectifier is used as the scavenging interface, then the circuit structure is simple and passive, but the coupling efficiency between transducer and interface is low and cannot be actively optimized
Solution Approach 1:
The patent replaces the passive diode-bridge rectifier (mechanical/electrical component-based system) with an active switching circuit controlled by a microcontroller. This substitution enables dynamic impedance matching and active optimization of power transfer, resolving the contradiction between structural simplicity and coupling efficiency by trading physical complexity for controllable performance.
Solution Approach 2:
The patent dynamically changes the operating parameters (switching timing, duty cycle) of the rectifier circuit based on real-time conditions. By adjusting these parameters, the system optimizes the coupling efficiency between transducer and scavenging interface while maintaining a relatively simple overall structure, thus resolving the contradiction between simplicity and efficiency.
2Adaptability or versatility
If the transducer signal amplitude is low, then the system can operate with smaller mechanical inputs, but the diode-bridge rectifier cannot harvest energy effectively due to voltage threshold limitations
Solution Approach 1:
The patent replaces the diode-based passive rectification mechanism with an active switching circuit that can operate at arbitrarily low voltages. The MOSFETs in the switching circuit have negligible voltage drops compared to diodes, enabling energy harvesting from low-amplitude transducer signals that would otherwise be insufficient to overcome diode threshold voltages.
Solution Approach 2:
The control unit monitors the transducer output and automatically adjusts the switching circuit operation to match the available signal amplitude. This self-adjusting mechanism enables the system to harvest energy across a wide range of input conditions, from low-amplitude vibrations to high-amplitude inputs, maintaining adaptability while preventing energy loss.
3Loss of energy
If impedance matching is optimized between transducer and scavenging interface, then power transfer is maximized, but the system complexity increases due to active control requirements
Solution Approach 1:
The microcontroller in the patent performs multiple functions: it controls the switching circuit for impedance matching, monitors system parameters, and adjusts operation based on varying conditions. This multi-functionality consolidates what would otherwise require separate dedicated circuits into a single integrated control unit, reducing overall system complexity while maintaining optimized power transfer.
Solution Approach 2:
The system implements feedback control where the microcontroller monitors the transducer output and adjusts the switching circuit parameters accordingly. This feedback mechanism automatically maintains optimal impedance matching without requiring complex external control systems, as the control is self-regulated based on real-time system state information.
4Loss of energy
If active control is implemented in the rectifier circuit, then power transfer efficiency is maximized through impedance matching, but the device complexity increases
Solution Approach 1:
The patent implements dynamic control of the rectifier circuit through a microcontroller that adjusts switching parameters in real-time. This dynamic approach enables the system to adapt to varying operating conditions and maintain optimal power transfer efficiency, while the digital control architecture provides flexibility without requiring complex analog circuitry.
Solution Approach 2:
The patent replaces complex analog impedance matching circuits with a digitally controlled switching system. The microcontroller implements the impedance matching algorithm through software, substituting what would otherwise require complex analog components and circuits with a simpler digital control approach that achieves the same or better performance.
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 achieves high efficiency in energy harvesting, exceeding 95% coupling efficiency and enabling energy recovery from low-amplitude signals, overcoming limitations of traditional diode-bridge rectifiers and ensuring optimal impedance matching.
Implementation Method 1
a transducer 2, for example of an electromagnetic or piezoelectric type, subject during use to environmental mechanical vibrations and configured for converting mechanical energy into electrical energy
Implementation Method 2
a transducer 2, for example of an electromagnetic or piezoelectric type, subject during use to environmental mechanical vibrations and configured for converting mechanical energy into electrical energy
Implementation Method 3
a first inductor 22b, having an input terminal 25' connected to the first input terminal 25' of the rectifier circuit 24 and a second terminal 26' connected to the first output terminal 26' of the rectifier circuit 24
Data Source
Figure 1~2
Figure 3
Figure 4a~4b
AI summary
An energy scavenging interface (24) having an input port (25', 25"), which can be connected to a storage element (22b) of a transducer that generates an electrical signal, and an output port (26', 26") for supplying an output signal (VOUT) to an electrical load (27, 28), comprising: a first switch (30) that receives the input signal; a second switch (36) that supplies the output signal; and a control logic (60) configured for: closing the first switch and opening the second switch for a first time interval having a first temporal duration (TDELAY); acquiring a scaled copy (Ip/K) of the peak value (Ip) of the electric current accumulated in the storage element during the first time interval; opening the first switch and closing the second switch (36) for supplying the electrical load; and keeping them in this state as long as the current value of the output signal (IOUT) is greater than the value of said scaled copy (Ip/K) of the peak value.