Rectifier Circuit with Dynamic Bulk Biasing for Low Power Efficiency
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Solution Overview
Problem
Current rectifier circuits face inefficiencies due to threshold voltages and reverse currents, which limit their ability to operate with low input powers and increase costs, especially in batteryless applications like wireless sensor networks.
Innovation Solution
A modified double-half-wave CMOS rectifier circuit that compensates for reverse currents without adding invasive elements, allowing operation with very low input powers by dynamically varying the threshold voltage to favor forward conduction and limit reverse conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional rectifier circuits are used, then the circuit structure is simple, but the efficiency is low due to threshold voltages and reverse currents
Solution Approach 1:
The rectifier circuit is divided into multiple cells (first cell, second cell, third cell, etc.) where each cell contains transistors with independently controlled bulks. This segmentation allows each cell to be optimized for reducing reverse currents while maintaining overall circuit simplicity through modular repetition of the same structure.
Solution Approach 2:
The bulk voltages of the transistors are dynamically varied to modulate threshold voltages during operation. By applying alternating bulk voltage signals (e.g., Vb1, Vb2, Vb3) to the transistor bulks, the threshold voltage changes over time to favor forward conduction and limit reverse conduction, thereby improving efficiency without adding permanent circuit elements.
2Loss of energy
If zero-threshold transistors are used, then the threshold voltage losses are reduced, but the manufacturing cost increases
Solution Approach 1:
Instead of using zero-threshold transistors which require special manufacturing processes, the invention changes the operating parameters by dynamically varying the bulk voltage of standard transistors. This parameter change effectively reduces the threshold voltage during forward conduction phases while maintaining compatibility with standard CMOS manufacturing processes, thus reducing costs.
Solution Approach 2:
The invention substitutes the physical modification of transistor structure (zero-threshold transistors requiring specialized fabrication) with an electrical control mechanism (dynamic bulk voltage application). This replaces a manufacturing-oriented solution with an operational control solution, maintaining ease of manufacture while achieving the desired threshold voltage reduction.
3Loss of energy
If additional circuit components are added to compensate reverse currents, then the efficiency improves, but the power losses increase
Solution Approach 1:
The rectifier circuit uses its own internal signals to compensate for reverse currents. The bulk voltage signals applied to the transistor bulks are generated from the same input signal that drives the rectifier, creating a self-service mechanism where the circuit compensates for its own deficiencies without requiring external auxiliary components that would introduce additional power losses.
Solution Approach 2:
The existing transistor structures in the rectifier circuit serve multiple functions: they perform the primary rectification function while simultaneously having their bulk terminals used for threshold voltage modulation to compensate reverse currents. This multi-functionality eliminates the need for separate compensation circuits, thereby avoiding additional power losses.
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 enhances the efficiency of the rectifier circuit, enabling it to function effectively with low input powers and reducing energy losses, thereby improving the overall performance and cost-effectiveness.
Implementation Method 1
each transistor comprising conduction control terminals acting on the bulks of the transistors for varying the threshold voltage of the transistors
Data Source
AI summary
A rectifier cell includes a first cell branch and a second cell branch that extend in parallel between two opposite nodes receiving an a.c. signal. The first cell branch includes a first pair of transistors arranged with their current paths cascaded, with a first intermediate point in-between. The second cell branch includes a second pair of transistors arranged with their current paths cascaded, with a second intermediate point in-between. Each of the pairs of transistors includes a first transistor with a control terminal coupled to one of the two opposite nodes and a second transistor with a control terminal coupled to the other of the two opposite nodes. The bulks of the transistors receive voltages in order to vary the transistor threshold voltage by bringing the threshold voltage to a first value during forward conduction and to a second value during reverse conduction.