Low-Drop Diode Equivalent Circuit for Vibration Energy Harvesting
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Solution Overview
Problem
Existing vibration energy harvesting systems face significant power loss due to diode drops in rectifier circuits, which are not efficiently addressed by current technologies that often require external power supplies, additional components, or standby power consumption.
Innovation Solution
A low-drop diode equivalent circuit using a MOSFET operated in the linear region, controlled to conduct with minimal voltage drop and block reverse conduction, powered directly from the input signal without external power, and integrated with a current reversal sense circuit to replace traditional diodes in full-wave bridge rectifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional diodes are used in rectifier circuits, then reverse conduction is blocked, but significant power loss occurs due to forward voltage drop
Solution Approach 1:
The patent changes the operating parameters of the MOSFET by controlling its gate voltage dynamically. During forward conduction, the gate is driven to achieve deep triode region operation with minimal voltage drop. During reverse blocking, the gate is controlled to create a high impedance state. This parameter modulation allows the single MOSFET to exhibit both low forward drop and reliable reverse blocking characteristics.
Solution Approach 2:
The patent introduces a control circuit as an intermediary between the input signal and the MOSFET gate. This control circuit processes the input signal to generate appropriate gate drive voltages that switch the MOSFET between conduction and blocking states. The control circuit acts as a mediator that enables the MOSFET to perform diode functions without requiring external power supplies or additional passive components.
2Loss of energy
If synchronous rectifiers with external power supply are used, then forward voltage drop is reduced, but additional power supply requirements and device complexity increase
Solution Approach 1:
The patent implements self-service by designing the control circuit to be powered directly from the input signal itself rather than requiring external power supplies. The control circuit extracts necessary power from the input signal to drive the MOSFET gate, eliminating the need for separate power sources. This self-powered approach reduces device complexity while maintaining low forward voltage drop performance.
Solution Approach 2:
The patent makes the control circuit multi-functional by using it both to drive the MOSFET gate for low drop conduction and to extract power from the input signal for self-biasing. The same control circuit performs multiple functions: signal processing, gate drive generation, and power management, thereby reducing overall device complexity without sacrificing performance.
3Device complexity
If passive full wave rectifier implementations are used, then external power supply is not required, but additional off-chip capacitors and standby power consumption are needed
Solution Approach 1:
The patent extracts and eliminates the need for additional off-chip capacitors by integrating all necessary capacitance within the chip using MOSFET gate capacitances and small on-chip capacitors. The design removes bulky external passive components while maintaining the required electrical characteristics for full-wave rectification operation.
Solution Approach 2:
The patent merges the functions of multiple separate components into a single integrated circuit. The MOSFET, control circuit, and necessary capacitance are combined into one chip, eliminating the need for separate off-chip capacitors and reducing standby power consumption. The control circuit and power management functions are merged to achieve self-powered operation without additional components.
4Power
If MOSFET is operated in saturation region, then high current capability is achieved, but reverse conduction occurs and power efficiency decreases
Solution Approach 1:
The patent applies dynamic operation by continuously adjusting the MOSFET's operating region through controlled gate voltage. Rather than operating statically in saturation, the MOSFET is dynamically switched between triode region during forward conduction and a high-impedance state during reverse blocking. This dynamic control eliminates reverse conduction losses while maintaining high current capability during the conduction phase.
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
The solution significantly reduces diode drop voltage, increases output power efficiency, and eliminates the need for external power supplies and additional components, achieving up to 169% higher output power compared to conventional diode-connected MOSFETs while maintaining low power consumption.
Implementation Method 1
A low drop diode equivalent circuit, input is the source terminal of a metal oxide semiconductor field effect transistor (MOSFET) (M1), output is the drain terminal of M1 and the gate terminal of M1 is provided a control signal
Implementation Method 2
base terminal of said sense transistor is coupled to the output, collector terminal of said sense transistor is connected to base terminal of a control BJT (T2)
Implementation Method 3
Piezoelectric harvesters work by stressing a piezoelectric material in accordance with the vibration and tapping the generated electric charge from the material
Implementation Method 4
Electromagnetic device based harvesters employ a coil to tap energy from a moving magnetic field produced by magnets, which move in the ambient vibration
Implementation Method 5
In electrostatic energy transducers, vibration leads to a relative parallel motion between an electret and nearby metallic surface. This leads to induced counter charge on the metal, with the charge simply following the relative motion of the electrets. This produces an electric current
Data Source
AI summary
Embodiments of the disclosure relate to a low drop diode equivalent circuit. Piezoelectric device based vibration energy harvesting requires a rectifier for conversion of input ac to usable dc form. Power loss due to diode drop in rectifier is a significant fraction of the already low levels of harvested power. The low-drop-diode equivalent can replace the rectifier diodes and minimize power loss. The diode equivalent mimics a diode using linear region operated MOSFET. The diode equivalent is powered directly from input signal and requires no additional power supply for its control. Power used by the control circuit is kept at a value which gives an overall output power improvement. The diode equivalent replaces the four diodes in a full wave bridge rectifier, which is the basic full-wave rectifier and is a part of the more advanced rectifiers like switch-only and bias-flip rectifiers.