Semiconductor Drive Circuit Using AC Pulse Transformer
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Solution Overview
Problem
Existing drive circuits for semiconductor switching devices face challenges in achieving fast switching and isolation with limited drive voltage, particularly for next-generation devices like SiC-J FETs and GaN FETs, which require high-speed switching and are restricted by zener diode voltage limitations and increased costs due to dual gate drive power supplies.
Innovation Solution
A semiconductor switching device drive circuit that includes a drive power supply, an alternating current generation unit, and a transformer with primary and secondary windings, where first and second switching devices are inserted oppositely in the current path, connected in parallel with diodes, allowing for voltage-driven operation and alternating current-induced switching without the need for zener diodes, enabling efficient isolation and high-speed switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If zener diodes are used to regulate secondary voltage in pulse transformer-based gate drive circuits, then isolation is achieved, but the gate voltage is limited and cannot be decreased below the zener voltage threshold
Solution Approach 1:
The patent removes zener diodes from the gate drive circuit, extracting the voltage regulation function to a separate resistive divider network on the primary side of the pulse transformer. This allows the secondary voltage to be determined by transformer turns ratio rather than being constrained by zener diode breakdown voltage, enabling flexible gate voltage control below zener thresholds while maintaining isolation.
Solution Approach 2:
The patent introduces a resistive divider network as an intermediary element on the primary side of the pulse transformer to set the gate drive voltage. This mediator allows voltage regulation without directly constraining the secondary voltage, enabling the use of lower-voltage gate drivers with high-side switches while maintaining proper isolation through the transformer.
2Adaptability or versatility
If two gate drive power supplies are used in pulse transformer configurations, then PWM control capability is achieved, but circuit complexity and cost increase
Solution Approach 1:
The patent merges the functions of multiple power supplies into a single gate drive power supply. By using a pulse transformer with primary-side voltage regulation, the circuit achieves both high-side and low-side driver functionality from one power source, eliminating the need for dual isolated power supplies while maintaining PWM control capability through the transformer's isolation and voltage transformation properties.
Solution Approach 2:
The single gate drive power supply is designed to serve multiple functions: providing voltage for both high-side and low-side switches, enabling PWM control, and maintaining isolation through the pulse transformer. This universal power supply approach replaces the need for specialized dual power supplies, reducing complexity while preserving full PWM functionality.
3Speed
If high voltage (10V to 20V) is applied to the gate of Si power MOSFETs, then fast switching is achieved, but next-generation devices like SiC-J FET and GaN FET cannot be driven at high voltage
Solution Approach 1:
The patent changes the voltage parameter control approach by using a pulse transformer with adjustable turns ratio and primary-side resistive divider networking. This allows the secondary voltage to be precisely controlled at low levels (2V-3V) suitable for SiC-J FET and GaN FET gates, while still achieving fast switching through optimized pulse transformation and gate charge delivery, rather than relying on high continuous voltage.
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 allows for efficient clamping of the control terminal potential, enabling fast switching and reduced voltage requirements, while eliminating the need for zener diodes and dual gate drive power supplies, thus enhancing operational safety and reducing costs.
Implementation Method 1
a transformer Tr1 having a primary winding N1 supplied with the alternating current and a secondary winding N2 generating an alternating-current voltage
Data Source
AI summary
One of first and second switching devices turns on to flow a current along a current path between a potential reference output terminal of a drive-target switching device and a control terminal of the drive-target switching device to turn on the drive-target switching device. Thereby, a voltage changes between the control terminal of the drive-target switching device and the potential reference output terminal of the drive-target switching device to turn off the one of the first and second switching devices being turned on. Thereby, a potential of the control terminal of the drive-target switching device is clamped.