Synchronous Rectifier DC-DC Converter for Induction Energy Harvesting
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Solution Overview
Problem
Induction energy harvesting devices face inefficiencies due to losses in rectifier diodes and the need for expensive external inductors, and struggle with harvesting low AC voltage levels at low vibration levels.
Innovation Solution
The implementation of active rectifying circuitry using synchronous switches and a switch controller to manage AC energy harvesting, allowing for efficient conversion and storage of energy without the need for external inductors, and enabling efficient harvesting of low AC voltage levels through adaptive switching strategies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If passive rectifier diodes are used in the power management circuit, then the circuit structure is simple, but the harvesting efficiency is low due to voltage losses in the diodes
Solution Approach 1:
The patent replaces passive rectifier diodes with active synchronous switching circuitry consisting of MOSFETs (Q1-Q4) controlled by a microcontroller. This substitution eliminates the inherent voltage drop losses associated with diode forward voltage, thereby significantly improving harvesting efficiency while maintaining manageable circuit complexity through integrated control.
Solution Approach 2:
The patent changes the operating parameters of the rectification process by using actively controlled switches instead of passive diodes. The MOSFETs are controlled to achieve near-zero voltage drop during rectification, transforming the rectification process from a passive high-loss operation to an active low-loss operation, thereby improving overall system efficiency.
2Reliability
If a boost type DC-DC converter is used to improve low-vibration-level harvesting capability, then the voltage buildup is improved, but external inductors are required which increase cost and complexity
Solution Approach 1:
The patent makes the harvester coil serve dual functions: it acts as both the sensing element for vibration detection and as the inductor for the boost DC-DC converter. This eliminates the need for a separate external inductor, reducing component count, cost, and complexity while maintaining the ability to harvest energy at low vibration levels through the boost conversion mechanism.
Solution Approach 2:
The patent merges the function of the harvester coil with the inductor function of the DC-DC converter. By combining these two functions into a single component, the system achieves boost conversion capability for improved low-vibration harvesting without requiring additional external inductors, thereby simplifying the overall device architecture.
3Power
If the output impedance of the energy harvester and input capacitance of storage circuitry form an RC network, then the voltage establishment is determined by the time constant, but at low vibration levels it takes several minutes to accumulate sufficient energy
Solution Approach 1:
The patent employs periodic switching action through the synchronous rectifier and boost converter control to actively pump energy into the storage capacitor. Instead of relying on passive RC charging, the periodic switching of MOSFETs Q1-Q4 and the boost converter operation create forced energy transfer cycles that rapidly charge the storage capacitor even at low vibration levels, dramatically reducing the time to accumulate sufficient energy.
Solution Approach 2:
The patent ensures continuous energy transfer to the storage capacitor through the boost converter operation. The converter maintains continuous conduction mode where energy is continuously extracted from the harvester coil and transferred to the storage capacitor, eliminating the intermittent charging behavior of passive RC networks and enabling rapid energy accumulation even when vibration levels are low.
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 enhances the efficiency of energy harvesting by minimizing voltage losses and eliminating the requirement for external inductors, thereby improving the overall performance and cost-effectiveness of induction energy harvesting systems, especially at low vibration levels.
Implementation Method 1
When coil 4 and associated mass m move with velocity v in the magnetic field, their kinetic energy Ek=(mv2)/2 is transformed into potential energy in spring 2 which then is converted into electromagnetic energy ELh=eLh=(LhILh2)/2. The electromotive force eL in the coil is defined by the velocity v of its movement through the magnetic field, and is given by eL=−w×B×v
Data Source
AI summary
A system for managing AC energy harvested from a harvesting device (1) including a coil (4) including switching circuitry (S1-S4) coupled between first (7A) and second (7B) terminals of the coil. The switching circuitry includes first (S1), second (S2), third (S1), and fourth (S4) switches. A switch controller (17) closes the second and fourth switches to allow build-up of current (ILh) in the coil, opens one of the second and fourth switches, and closes a corresponding one of the third and first switches in response to the built-up inductor current reaching a predetermined threshold value (Ihrv) to steer the built-up inductor current through the corresponding one of the third and first switches to a current-receiving device (24 and/or RL, CL).