Half-Bridge Transistor Circuit Without 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
1Ease of operation
If separate anti-parallel diodes are added to each transistor in the bridge circuit, then the circuit can properly conduct current in both directions, but the device complexity increases and power dissipation increases due to poor switching characteristics of parasitic diodes
Solution Approach 1:
The patent combines the transistor and anti-parallel diode into a single integrated switch component. The transistor provides voltage blocking capability while the integrated diode handles reverse current conduction, eliminating the need for separate external diodes and reducing overall circuit complexity.
Solution Approach 2:
The integrated switch component performs multiple functions: it blocks high voltage in the OFF state (transistor function) and conducts reverse current in the OFF state (diode function). This multi-functional component replaces what previously required separate transistor and diode components.
2Ease of operation
If separate anti-parallel diodes are added to each transistor in the bridge circuit, then the circuit can properly conduct current in both directions, but power dissipation increases due to inherent poor switching characteristics of parasitic diodes
Solution Approach 1:
The patent modifies the switching parameters and characteristics of the integrated diode to achieve faster switching speeds and lower on-resistance. By optimizing the diode's electrical parameters, the power dissipation during switching transitions and conduction is significantly reduced compared to conventional parasitic diodes.
3Stress or pressure
If traditional IGBTs with anti-parallel diodes are used, then the switches can block high voltage, but shoot-through currents from high-voltage supplies occur due to timing issues
Solution Approach 1:
The integrated switch is designed with built-in protection mechanisms that preemptively prevent shoot-through currents. The gate drive circuitry incorporates timing control that ensures one switch is fully off before the other turns on, and the integrated diode's fast recovery characteristics prevent reverse recovery shoot-through currents.
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 motor drives and other power circuits.
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
capable of conducting current in both directions through the channel when biased in an ON state
Implementation Method 3
inductive loads, i.e., inductive components such as motor coils
Implementation Method 4
the inductive component 21 forces the voltage at node 17 to a sufficiently negative value to cause diode 52 to conduct
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.