GaN Switching Circuit Current Limiting for Drain Negative Voltage
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Solution Overview
Problem
The use of GaN power transistors in switching circuits can result in large negative voltages at the drain terminal, which can cause damage or abnormal operation of the controller due to unregulated negative currents.
Innovation Solution
A current limiting circuit is introduced, which connects a diode or zener diode between the drain of the main power transistor and the power supply terminal of the controller, or uses a series of auxiliary diodes and a main diode, to limit negative currents and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If power is obtained directly from the drain pin of a GaN power transistor, then the controller can be simplified, but large negative voltage appears at the drain terminal causing damage to the controller
Solution Approach 1:
The patent introduces a current limiting circuit as an intermediary component between the drain terminal and the controller's power supply terminal. This circuit includes a first resistor and a second resistor connected in series, which limits the negative current flowing to the controller while still allowing power transfer, thus resolving the contradiction between simplification and protection
Solution Approach 2:
The patent applies beforehand cushioning by pre-configuring the current limiting circuit to absorb and limit negative voltage spikes before they can reach and damage the controller. The resistors are positioned in advance to cushion the harmful voltage effects during reverse current flow
2Loss of energy
If an anti-parallel diode is integrated (as in power MOSFET), then reverse current voltage drop is reduced, but GaN power transistors lack such diode causing large voltage drop and negative voltage issues
Solution Approach 1:
The patent extracts the protective function of the anti-parallel diode from the power transistor structure itself and implements it separately through the current limiting circuit. Since GaN transistors cannot integrate the diode, the patent takes out the protection function and realizes it through external passive components (resistors) that limit reverse current effects
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 current limiting circuit effectively prevents large negative voltages or currents from reaching the controller, thereby ensuring normal operation and preventing damage to the controller.
Implementation Method 1
the current limiting circuit may include a diode. The diode may include an anode connected with the drain of the main power transistor, and a cathode connected with the power supply terminal of the controller
Implementation Method 2
the current limiting circuit may include a zener diode. The zener diode may include an anode connected with the drain of the main power transistor, and a cathode connected with the power supply terminal of the controller
Data Source
AI summary
A current limiting circuit of a switching circuit, and a switching circuit are provided. The switching circuit uses a gallium nitride (GaN) power transistor as a main power transistor. The current limiting circuit includes a first terminal connected with a drain of the GaN power transistor, and a second terminal connected with a controller of the switching circuit. The current limiting circuit is configured to limit a current flowing out of a power supply terminal of the controller. The current limiting circuit suppresses a negative current flowing through the controller.