Synthetic Diode Rectifier Low Forward Voltage Drop
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Solution Overview
Problem
Existing rectifiers in AC-to-DC converters experience significant power loss due to forward voltage drops across diodes, which current technologies have not adequately addressed, leading to inefficiencies in energy conversion.
Innovation Solution
A synthetic diode rectifier circuit comprising a first and second Field Effect Transistor (FET), a sense resistor, and a comparator, where the gates of the FETs are coupled together, and the sense resistor is placed in a current path that bypasses the first FET, allowing the second FET to handle current flow with minimal voltage drop, effectively reducing the forward voltage drop across the rectifier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a standard diode is used in a rectifier, then the rectifier structure is simple, but the forward voltage drop is high (about 1 volt at peak current), causing significant power loss
Solution Approach 1:
The rectifier circuit is segmented into multiple functional blocks: a synthetic diode circuit replacing individual diodes, a voltage detector circuit for control, and a transistor switching mechanism. This segmentation allows each block to perform its specific function optimally, achieving low forward voltage drop while maintaining overall system manageability
Solution Approach 2:
A voltage detector circuit acts as an intermediary between the AC input and the transistor switching mechanism. It detects the polarity of the input voltage and controls the transistor accordingly, enabling the synthetic diode to achieve diode-like rectification with much lower forward voltage drop (0.04V) than standard diodes
2Loss of energy
If a synthetic diode circuit with field effect transistor is used, then the forward voltage drop is reduced to 0.04V, but the circuit complexity increases due to additional control components
Solution Approach 1:
The voltage detector circuit automatically detects the input voltage polarity and self-regulates the transistor switching without external control signals. The circuit serves itself by using the input voltage characteristics to control its own operation, eliminating the need for complex external control mechanisms
Solution Approach 2:
The synthetic diode circuit merges the functionality of a standard diode with a transistor switching mechanism into a single integrated unit. The voltage detector and transistor are combined to create a unified synthetic diode that performs both detection and switching functions, reducing overall system complexity despite the advanced functionality
3Loss of energy
If bipolar transistor with parallel diode is used, then forward voltage drop is reduced to 0.1 volts, but the circuit requires complex associated circuitry for control
Solution Approach 1:
The patent replaces the mechanical/control-based switching mechanism with an electric field-controlled field effect transistor. The voltage detector circuit uses electrical signals to control the FET switching, substituting complex control circuitry with a simpler electric field-based control mechanism that achieves the same rectification function with lower forward voltage drop
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 synthetic diode rectifier circuit achieves a forward voltage drop of approximately 0.4 volts, significantly lower than standard diodes, thereby reducing power loss and improving energy conversion efficiency while maintaining the ability to block high reverse voltages.
Implementation Method 1
the sense resistor is disposed in a current path that extends from an anode terminal of the rectifier circuit, through the sense resistor, to the source of the second FET, through a body diode of the second FET, to the drain of the second FET
Implementation Method 2
a comparator. The gates of the first and second FETs are coupled together, and the drains of the first and second FETs are coupled together
Data Source
AI summary
A rectifier includes a larger Field Effect Transistor (FET1) and a smaller FET (FET2). A sense resistor is in series with FET2's body diode between a cathode terminal and an anode terminal. If the cathode terminal voltage is greater than the voltage on the anode terminal, then body diodes of FETs are reverse biased, the FETs are controlled to be off, and there is no current flow through the rectifier. If, however, the voltage on the anode terminal becomes positive with respect to the cathode terminal, then the body diode of FET2 starts to conduct and there is a voltage drop across the sense resistor. A comparator detects this condition and turns both FETs on. The rectifier is then conductive, so current can flow from the anode terminal, through the larger FET1, and to the cathode terminal, with a small forward voltage drop and without passing across the sense resistor.