Half-Bridge MOSFET Circuit Without Separate Anti-Parallel Diodes
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Solution Overview
Problem
Traditional bridge circuits require separate anti-parallel diodes for proper operation, which lead to increased complexity and power dissipation due to the inherent poor switching characteristics of parasitic diodes, and are prone to shoot-through currents from high-voltage supplies.
Innovation Solution
A half bridge circuit design utilizing a single transistor that can operate in multiple modes to block voltage, conduct current in both directions, and function as both a switching transistor and a diode, eliminating the need for separate diodes and minimizing power dissipation by controlling gate voltages to prevent shoot-through currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate anti-parallel diodes are added to each transistor switch, then the circuit can properly conduct reverse current, but the device complexity and power dissipation increase due to poor switching characteristics of parasitic diodes
Solution Approach 1:
The patent merges the diode function into the transistor structure by utilizing the body diode inherent in the MOSFET device. Instead of adding separate anti-parallel diodes, the circuit leverages the existing parasitic diode structure within each MOSFET, thereby reducing component count while maintaining the necessary reverse current conduction capability.
Solution Approach 2:
The MOSFET device is made multi-functional by enabling it to operate both as a switching transistor and as a diode. The single MOSFET performs dual roles: active switching when the gate is driven, and passive reverse current conduction when the body diode conducts, eliminating the need for separate dedicated diode components.
2Reliability
If separate anti-parallel diodes are added to each transistor switch, then reverse current conduction is enabled, but power dissipation increases due to poor switching characteristics
Solution Approach 1:
The patent merges the diode function into the transistor structure by utilizing the body diode inherent in the MOSFET device. Instead of adding separate anti-parallel diodes, the circuit leverages the existing parasitic diode structure within each MOSFET, thereby reducing component count while maintaining the necessary reverse current conduction capability.
3Power
If traditional IGBTs with anti-parallel diodes are used, then the circuit can block high voltage and conduct current, but the device complexity and power loss increase
Solution Approach 1:
The MOSFET device is made multi-functional by enabling it to operate both as a switching transistor and as a diode. The single MOSFET performs dual roles: active switching when the gate is driven, and passive reverse current conduction when the body diode conducts, eliminating the need for separate dedicated diode components.
4Reliability
If multiple components (transistor and separate diode) are used in each switch, then proper current conduction is achieved, but the switch configuration becomes more complex
Solution Approach 1:
The patent merges the diode function into the transistor structure by utilizing the body diode inherent in the MOSFET device. Instead of adding separate anti-parallel diodes, the circuit leverages the existing parasitic diode structure within each MOSFET, thereby reducing component count while maintaining the necessary reverse current conduction capability.
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 design simplifies the switch configuration, reduces power loss, and prevents shoot-through currents by allowing the transistor to perform dual roles, thereby enhancing the operational efficiency of bridge circuits in motor drives and other power applications.
Implementation Method 1
The transistors 41-46 are each capable of blocking a voltage at least as large as the high voltage (HV) source of the circuit 10 when they are biased in the OFF state
Implementation Method 2
in a second mode of operation of conducting substantial current in the at least one direction through the channel
Implementation Method 3
in a third mode of operation of conducting substantial current in an opposite direction through the channel
Implementation Method 4
controlling gate voltages to prevent shoot-through currents
Data Source
AI summary
A half bridge is described with at least one transistor having a channel that is capable in a first mode of operation of blocking a substantial voltage in at least one direction, in a second mode of operation of conducting substantial current in one direction through the channel and in a third mode of operation of conducting substantial current in an opposite direction through the channel. The half bridge can have two circuits with such a transistor.