GaN Bias Sequencing Circuit for Safe Drain and Gate Power Switching
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Solution Overview
Problem
GaN RF power transistors face damage during power-on and power-off stages due to improper sequencing of bias voltages and currents, with issues of inrush current and temperature drift in existing circuits.
Innovation Solution
The proposed circuitry includes a negative bias circuit, a drain switch circuit, and a control circuit that manages the gate and drain voltages to ensure safe power-up and power-down sequences, using a buck-boost power supply and capacitors to regulate currents and voltages, and a voltage holding circuit to prevent damage during shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high positive voltage is applied quickly to the drain, then power-on speed is improved, but inrush current increases and damages the GaN transistor
Solution Approach 1:
The control circuit applies negative bias voltage to the gate before applying high positive voltage to the drain. This preliminary action prepares the GaN transistor by establishing the gate voltage first, ensuring the device is ready to handle the subsequent high voltage without generating excessive inrush current, thus resolving the contradiction between fast power-on and current protection
2Object-generated harmful factors
If high positive voltage is turned off slowly, then inrush current is reduced, but the GaN transistor may be damaged in the power-off stage
Solution Approach 1:
The control circuit turns off the high positive voltage on the drain before completely removing the negative bias voltage from the gate. This preliminary action ensures that the drain voltage is reduced to zero while the gate still maintains its negative bias, preventing any potential damage during the power-off transition and solving the contradiction between slow voltage reduction and device protection
3Reliability
If negative bias voltage is increased to provide sufficient current, then transistor protection is improved, but power consumption increases
Solution Approach 1:
The control circuit dynamically adjusts the magnitude of the negative bias voltage based on the operational state of the GaN transistor. During normal operation, an adequate negative bias is maintained for protection. During idle or low-power states, the negative bias magnitude is reduced, thereby lowering power consumption while maintaining sufficient protection levels when needed
Data Source
AI summary
Embodiments of the present disclosure provide circuitry and a method for a gallium nitride (GaN) device. The circuitry includes a negative bias circuit configured to provide a negative bias voltage for a gate of the GaN device; a drain switch circuit configured to turn on or off a positive voltage for a drain of the GaN device; and a control circuit configured to control the drain switch circuit based on provision of the negative bias voltage, such that the positive voltage for the drain is turned on after a voltage of the gate reaches the negative bias voltage and turned off before the negative bias voltage completely disappears.