GaN Half-Bridge Bootstrap Circuit Without Parallel Diode
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Solution Overview
Problem
Existing half bridge power conversion circuits using GaN devices face challenges in efficiently managing voltage transitions and preventing shoot-through conditions due to high dv/dt effects, leading to inefficiencies and potential damage from false triggering.
Innovation Solution
A GaN half bridge circuit with a bootstrap power supply voltage generator that includes a switch node, a bootstrap transistor, and a bootstrap capacitor, where the bootstrap transistor drive circuit controls the gate voltage to prevent shoot-through by ensuring the bootstrap capacitor is connected to a fixed voltage power supply only when necessary, eliminating the need for a diode in parallel with the bootstrap transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diode is added in parallel with the bootstrap transistor to prevent shoot-through, then reliability improves, but device complexity increases
Solution Approach 1:
The patent removes the diode component from the bootstrap circuit, extracting the harmful element that caused shoot-through conditions. The bootstrap transistor operates alone without the parallel diode, eliminating the complexity and reliability issues associated with the diode-transistor parallel configuration while maintaining shoot-through prevention through controlled gate voltage timing.
Solution Approach 2:
The bootstrap transistor is designed to self-regulate its operation through controlled gate voltage application. The gate voltage is applied only during specific switching transitions when needed, allowing the transistor to prevent shoot-through conditions autonomously without requiring additional protective components like diodes.
2Reliability
If the bootstrap transistor is continuously connected to the power supply, then power voltage stability improves, but power dissipation increases
Solution Approach 1:
The bootstrap transistor is activated periodically rather than continuously - specifically during the transition when the switching node voltage changes from the first voltage level to the second voltage level. The gate voltage is applied only during these specific transition periods, creating a periodic action pattern that maintains voltage stability when needed while minimizing power dissipation during steady-state operation.
Solution Approach 2:
The gate voltage is applied in advance of the actual switching event that requires bootstrap capacitor charging. By anticipating the voltage transition and pre-applying gate voltage, the system ensures the bootstrap capacitor is ready to provide stable voltage exactly when needed, rather than maintaining continuous connection.
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 efficiency by preventing shoot-through conditions and reducing power dissipation, while ensuring reliable operation by controlling voltage transitions effectively within the GaN half bridge circuit.
Implementation Method 1
a bootstrap capacitor connected to the switch node and to the bootstrap transistor, where the bootstrap capacitor is configured to supply the first power voltage while the voltage at the switch node is equal to the second switch node voltage
Implementation Method 2
the bootstrap transistor is configured to electrically connect the bootstrap capacitor to a power node at a second power voltage while the voltage at the switch node is equal to the first switch node voltage
Data Source
AI summary
A GaN half bridge circuit is disclosed. The circuit includes a bootstrap power supply voltage generator is configured to supply a first power voltage and includes a switch node. The circuit also includes a bootstrap transistor, a bootstrap transistor drive circuit, and a bootstrap capacitor connected to the switch node and to the bootstrap transistor. The bootstrap capacitor is configured to supply the first power voltage while the voltage at the switch node is equal to the second switch node voltage, the bootstrap transistor is configured to electrically connect the bootstrap capacitor to a power node at a second power voltage while the voltage at the switch node is equal to the first switch node voltage, and the bootstrap power supply voltage generator does not include a separate diode in parallel with the drain and source of the bootstrap transistor.