GaN Half-Bridge Driver Circuit Bootstrap Voltage Regulation
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Solution Overview
Problem
Existing high-voltage half-bridge switching circuits with GaN power transistors face inefficiencies and robustness issues due to unsatisfactory performance in bootstrap voltage management, particularly in maintaining gate-source voltage within optimal ranges and handling recirculating currents.
Innovation Solution
A half-bridge switching circuit with a current limiter circuit and active diode circuitry in the floating section, coupled with a bootstrap diode, to regulate the bootstrap voltage and prevent overcharging, ensuring efficient operation and robustness by limiting current flow and reducing voltage drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bootstrap circuit is used to provide floating supply voltage for the high-side driver, then the high-side switch can be controlled properly, but the bootstrap voltage may exceed optimal ranges causing inefficiency and robustness issues
Solution Approach 1:
The current limiter circuit continuously monitors the bootstrap voltage level and provides feedback control. When the bootstrap voltage reaches a threshold value, the circuit automatically activates to limit further current flow, maintaining the voltage within optimal ranges and preventing overcharging that would reduce efficiency.
Solution Approach 2:
The patent replaces passive bootstrap voltage regulation with an active electronic control system. The current limiter circuit uses electronic switching elements (such as MOSFETs or transistors) to dynamically control current flow, substituting passive components with active electronic regulation for more precise and efficient voltage management.
2Power
If the bootstrap voltage is allowed to rise freely, then the high-side driver receives sufficient power, but overvoltage events occur causing robustness issues
Solution Approach 1:
The current limiter circuit is designed to activate before dangerous overvoltage conditions can develop. By monitoring the bootstrap voltage and preemptively limiting current flow when threshold values are approached, the circuit prevents overvoltage events before they can compromise the robustness of the high-side driver or switch.
Solution Approach 2:
The circuit incorporates protective mechanisms that cushion against potential overvoltage damage. The current limiter acts as a preventive measure, ready to intervene and protect the high-side driver from voltage spikes or excessive voltage conditions that could occur during normal operation.
3Device complexity
If conventional power transistors are used instead of GaN transistors, then the circuit is simpler, but switching speed and efficiency are reduced
Solution Approach 1:
The patent changes the material parameter of the power transistor from conventional silicon-based materials to gallium nitride (GaN). This material parameter change enables significantly higher switching speeds and improved efficiency. The accompanying current limiter circuit is specifically designed to work with GaN transistors, providing precise voltage control that maximizes their performance capabilities.
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 solution effectively maintains the gate-source voltage within optimal ranges, enhancing efficiency and robustness by preventing overvoltage events and improving power handling during recirculating current conditions.
Implementation Method 1
a bootstrap diode having an anode coupled to the first input supply node and a cathode coupled to an intermediate supply node
Implementation Method 2
The current limiter circuit may be configured to sense the floating supply voltage and to counter a current flow from the intermediate supply node to the floating supply node as a result of the floating supply voltage reaching a threshold value
Data Source
AI summary
A circuit comprises first and second input supply nodes configured to receive a supply voltage therebetween. The circuit comprises a high-side driver circuit configured to be coupled to a high-side switch and produce a first signal between first and second high-side output nodes. The circuit comprises a low-side driver circuit configured to be coupled to a low-side switch and produce a second signal between first and second low-side output nodes. The circuit comprises a floating node configured to receive a floating voltage applied between the floating node and the second high-side output node, a bootstrap diode between the first input supply node and an intermediate node, and a current limiter circuit between the intermediate node and the floating node and configured to sense the floating voltage and counter a current flow from the intermediate node to the floating node as a result of the floating voltage reaching a threshold value.