RF Power Supply Gate Drive Using GaNFETs for Dead-Time Stability
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Solution Overview
Problem
Existing radio-frequency power supply devices face challenges in achieving high accuracy and reproducibility in dead time and pulse width control for LDMOSFETs, particularly at high-output/high-frequency radio frequencies, due to individual differences in propagation delay and high-frequency resonance issues.
Innovation Solution
The use of LDMOSFETs as amplifying elements and GaNFETs as switching elements in the gate drive unit, along with configurations to minimize propagation delay fluctuations and suppress high-frequency resonance, including drain resistance, limited wiring inductance, and symmetrical circuit arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If LDMOSFETs are used as amplifying elements for high-speed/radio-frequency operation, then high-speed operation characteristics are improved, but individual differences in propagation delay cause poor accuracy and reproducibility in dead time and pulse width control
Solution Approach 1:
A delay time adjustment circuit is introduced as an intermediary component between the control signal source and the LDMOSFET gate drive. This circuit includes adjustable delay elements that compensate for individual propagation delay differences in each LDMOSFET, allowing precise control of dead time and pulse width despite variations in transistor characteristics.
Solution Approach 2:
The delay time adjustment circuit enables dynamic modification of signal timing parameters to match the specific propagation characteristics of each LDMOSFET. By adjusting delay time parameters, the system achieves consistent dead time and pulse width control across multiple amplifying elements with different propagation delays.
2Ease of operation
If conventional sinusoidal gate signals are used for LDMOSFET switching, then linear amplification is achieved, but abnormal oscillation occurs during OFF interval and switching mode operation is not enabled
Solution Approach 1:
The gate signal waveform is dynamically changed from sinusoidal to rectangular wave based on the desired operating mode. The control system can switch between different gate drive waveforms to enable either linear amplification or switching mode operation, adapting the signal characteristics to the operational requirements.
Solution Approach 2:
The gate signal parameters including waveform shape, frequency, and amplitude are made adjustable. This allows the system to use sinusoidal signals for linear amplification when needed, while switching to rectangular wave signals with optimized parameters for efficient switching mode operation without abnormal oscillations.
3Power
If high-output/high-frequency radio frequency operation is implemented, then output power and frequency are improved, but high-frequency resonance issues and propagation delay fluctuations worsen
Solution Approach 1:
A feedback mechanism is implemented that monitors the actual dead time and pulse width at high frequencies and adjusts the delay time adjustment circuit parameters accordingly. This closed-loop control compensates for propagation delay fluctuations and suppresses high-frequency resonance, maintaining stable operation at high output power and frequency.
Solution Approach 2:
The delay time adjustment circuit pre-compensates for high-frequency effects before signals are applied to the LDMOSFETs. By anticipating and correcting for propagation delay variations and resonance tendencies at high frequencies in advance, the system maintains stable timing control and prevents oscillation issues.
Data Source
AI summary
The radio-frequency power supply device of the present invention comprises: a radio-frequency amplification unit that carries out radio-frequency amplification by the switching operation of amplifying elements; and a gate drive unit that inputs a gate signal to the gate terminals of the amplifying elements in the radio-frequency amplification unit to drive the amplifying elements. The amplifying elements in the radio-frequency amplification unit are LDMOSFETs, and the switching elements in the gate drive unit are GaNFETs. By utilizing LDMOSFETs as the amplifying elements, a high-output/high-frequency radio-frequency is output, and by utilizing GaNFETs as the switching elements, individual differences in propagation delay in the switching elements are reduced, and the fluctuation in the dead time DT and pulse width Ton of the gate signal for carrying out PWM control are suppressed to improve accuracy and reproducibility, to improve high-speed response characteristics, and to suppress high-frequency resonance.