MOSFET Rectifier and Regulator Circuit for Biomedical Implants
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power management systems for biomedical implants face inefficiencies in rectifying and regulating high-frequency AC power, particularly in achieving high output voltages with minimal loss, which is crucial for implant circuits like electrical stimulators.
Innovation Solution
A method and system utilizing a metal-oxide-semiconductor field-effect transistor (MOSFET) with a biasing circuit and control circuit to regulate current transfer, where a biasing voltage is generated and applied to the MOSFET's body terminal, and the gate voltage is controlled to manage current flow based on input and output voltages, using an auxiliary rectifier with a Schottky diode or diode-connected NMOS transistor to minimize voltage drop.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional rectifier with p-n junction diodes is used to rectify high-frequency AC power, then the rectification function is achieved, but significant voltage drop and power loss occur due to the forward bias voltage of the diodes
Solution Approach 1:
The patent changes the operating parameters of the rectifier by using MOSFETs instead of conventional p-n junction diodes. The MOSFETs operate in different regions (linear region for rectification, saturation region for regulation) to achieve lower voltage drop and reduced power loss while maintaining the rectification function.
Solution Approach 2:
The patent employs a diode-connected NMOS transistor to create an artificial diode with controlled characteristics. This copied diode function allows for optimized performance with lower forward voltage drop compared to conventional p-n junction diodes, reducing power loss in the rectification process.
2Productivity
If the frequency of AC power delivery is increased to 13.56 MHz or higher, then wireless power transfer efficiency is improved, but rectification losses increase and achieving high output voltages becomes more difficult
Solution Approach 1:
The patent implements dynamic control of the MOSFET gate voltages to optimize rectification at high frequencies. The gate voltages are adjusted in real-time based on the input AC signal phase and amplitude, allowing the rectifier to maintain high efficiency at 13.56 MHz and higher frequencies while minimizing rectification losses.
Solution Approach 2:
The patent incorporates feedback control through the regulator circuit that monitors the output voltage and adjusts the MOSFET gate voltages accordingly. This feedback mechanism ensures optimal rectification performance at high frequencies by dynamically compensating for frequency-related losses and maintaining high power transfer efficiency.
3Power
If high DC supply voltages higher than the peak AC voltage on the implanted coil are required for implant circuits, then the power supply requirements of stimulator circuits are met, but conventional rectifier-regulator architectures cannot achieve the required output voltage
Solution Approach 1:
The patent divides the power conversion function into two independent stages: a rectifier stage using MOSFETs that can operate with high input voltages, and a regulator stage that steps down to the required output voltage. This segmentation allows the rectifier to capture the full peak AC voltage without the constraints of conventional integrated regulator designs, enabling output voltages higher than the peak-to-peak AC power.
Solution Approach 2:
The patent introduces an intermediate unregulated DC voltage stage between the AC input and the regulated DC output. This intermediate stage allows the system to first rectify the AC voltage to a high DC level using MOSFETs, then regulate it down to the required output voltage, thereby achieving output voltages that exceed what conventional direct regulation architectures can provide.
4Power
If a regulator circuit is added to control the output voltage, then the desired DC voltage level is achieved, but voltage drop across the regulator reduces the available output voltage
Solution Approach 1:
The patent implements dynamic control of the MOSFET gate voltages to optimize the voltage drop across the regulator. By adjusting the gate voltages based on the difference between input and output voltages, the system minimizes the voltage drop and associated power losses while maintaining the required output voltage level.
Solution Approach 2:
The patent changes the operating parameters of the regulator by using MOSFETs instead of conventional linear regulators. The MOSFETs can operate in different regions to optimize the voltage drop characteristics, and the gate voltage control allows for dynamic adjustment to minimize power losses while maintaining the desired output voltage.
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 enables efficient rectification and regulation of AC power with reduced losses, achieving output voltages higher than the peak-to-peak AC power while maintaining high power efficiency, even at high input frequencies.
Implementation Method 1
The rectifying is performed utilizing a Schottky diode
Implementation Method 2
regulating transfer of current from the first terminal of the MOSFET to the second terminal of the MOSFET
Implementation Method 3
Inductive coupling is the most common method for delivering power wirelessly to implants from an external controller outside the body. The external controller usually includes (e.g., consists of) a coil driver driving a primary coil, which is inductively coupled to a secondary coil inside the implant
Data Source
AI summary
Systems and methods for rectifying and regulating an input voltage are disclosed. A biasing circuit is configured to generate a biasing voltage greater than the maximum value of the input voltage minus a forward bias voltage of a p-n junction diode and apply the biasing voltage to the body terminal of a MOSFET. The biasing circuit may generate the biasing voltage by rectifying the input voltage. A control circuit is configured to generate a gate voltage based on the rectified and regulated output voltage and apply the gate voltage to the gate terminal of the MOSFET.