SiC BJT Rectifier Circuit for Low Voltage Efficiency

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Solution Overview

Problem

Full wave rectifier circuits using silicon diodes and MOSFETs face efficiency limitations due to threshold forward voltage and temperature constraints, especially in low voltage applications, and are complex and costly.

Innovation Solution

The use of silicon carbide (SiC) bipolar junction transistors (BJTs) in rectifier circuits, which are configured to respond to AC input signals by forward and reverse biasing during different half cycles to generate a rectified output, potentially reducing complexity and enabling higher temperature operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If silicon diodes are used as rectifying elements, then the rectifier circuit can be simple in structure, but the efficiency is limited by threshold forward voltage especially in low voltage applications

Engineering Contradiction:

Improverectifier circuit structureVSAvoidforward voltage loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent changes the material parameter from silicon to silicon carbide (SiC), which fundamentally alters the electrical characteristics. SiC BJTs have lower threshold forward voltage and can operate efficiently at low voltages, directly addressing the energy loss problem while maintaining circuit simplicity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses silicon carbide (SiC) composite material for the BJT construction. SiC combines the benefits of wide bandgap semiconductor properties with bipolar junction transistor functionality, achieving both low voltage efficiency and simplified circuit operation without requiring additional MOSFET components

Inventive Principle:

Principle #40Composite materials

2Loss of energy

If MOSFET transistors are added across diodes to assist rectification, then forward conduction losses are reduced, but circuit complexity and cost increase

Engineering Contradiction:

Improveforward conduction lossVSAvoidrectifier circuit structure

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent merges the rectifying function and the low-loss switching function into a single SiC BJT component. The BJT inherently provides both rectification and low conduction loss characteristics, eliminating the need for separate MOSFETs and diodes, thus reducing circuit complexity while maintaining energy efficiency

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The SiC BJT serves multiple functions simultaneously: it acts as the rectifying element, the low-loss switching element, and the temperature-resistant component. This multi-functionality replaces the traditional combination of diodes and MOSFETs, achieving energy efficiency without increasing circuit complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Temperature

If silicon-based diodes and MOSFETs are used, then the rectifier circuit can operate at standard temperatures, but the temperature range is limited to below about 175° C.

Engineering Contradiction:

Improveoperating temperature rangeVSAvoidtemperature constraint

Core Design Contradiction:

TemperatureVSReliability

Solution Approach 1:

The patent changes the material composition from silicon to silicon carbide (SiC), which fundamentally changes the thermal properties. SiC has superior thermal stability and can operate reliably at temperatures above 175°C, directly expanding the operating temperature range while improving reliability in high-temperature environments

Inventive Principle:

Principle #35Parameter changes

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 configuration enhances the efficiency of rectification, reduces circuit complexity, and allows for higher temperature operation compared to traditional silicon-based rectifier circuits, making it suitable for low voltage applications.

Implementation Method 1

configured to respond to an alternating current (AC) input signal by forward biasing the SiC BJT circuit during a first half cycle of the AC input signal and to reverse bias the SiC BJT circuit during a second half cycle of the AC input signal

Methodology Applied

Scientific EffectForward biasing and reverse biasing: Diode

Data Source

PatentUS8218345B2Rectifier with SiC bipolar junction transistor rectifying elements

Publication Date: 2012.07.10 WOLFSPEED INC

AI summary

A rectifier circuit can include an input circuit and first and second silicon carbide (SiC) bipolar junction transistors (BJTs). The input circuit is configured to respond to an alternating current (AC) input signal by generating a first pair of opposite polarity AC signals and a second pair of opposite polarity AC signals. The first pair of AC signals has a greater voltage range than the second pair of AC signals. The first and second SiC BJTs each include an input terminal connected to receive a different one of the second pair of opposite polarity AC signals, a base terminal connected to receive a different one of the first pair of opposite polarity AC signals, and an output terminal connected to a rectified signal output node of the rectifier circuit. The input circuit is further configured to control the first and second SiC BJTs through the first and second pairs of opposite polarity AC signals to forward bias the first SiC BJT while reverse biasing the second SiC BJT during a first half cycle of the AC input signal and to reverse bias the second SiC BJT while forward biasing the second SiC BJT during a second half cycle of the AC input signal.