Level Shifter Circuit for High Voltage Control
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Solution Overview
Problem
High voltage semiconductor applications face limitations due to the use of high breakdown voltage transistors, which have poor figure of merit compared to GaN devices, leading to reduced operating frequencies and inefficiencies in power management systems.
Innovation Solution
A circuit arrangement and method utilizing low breakdown voltage transistors to control high side and low side devices in a stacked configuration, employing capacitive coupling and clamping circuitry to generate control signals that can handle high voltages without imposing those voltages on the transistors, enabling efficient control of high voltage devices with low voltage transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high breakdown voltage transistors are used to control high voltage devices, then the control circuit can handle high voltages, but the figure of merit deteriorates and operating frequency is limited
Solution Approach 1:
The patent introduces a level shifter circuit as an intermediary between the low voltage control signal and the high voltage device. This level shifter uses capacitive coupling to transfer the control signal across the high voltage potential difference without requiring the control transistors to withstand the full high voltage, thus enabling low voltage transistors with high figure of merit to control high voltage devices
Solution Approach 2:
The control circuit is segmented into multiple stages: a low voltage control stage using low voltage transistors with high figure of merit, and a high voltage output stage using the level shifter to provide the necessary high voltage control signal. This segmentation allows each stage to operate in its optimal voltage range, maintaining high operating frequency while achieving high voltage control capability
2Reliability
If high voltage transistors are used in control circuitry, then high voltage devices can be controlled, but the overall circuit performance is limited by the poor figure of merit of high voltage transistors
Solution Approach 1:
The level shifter acts as an intermediary that isolates the high voltage control path from the low voltage logic path. This allows low voltage transistors with high figure of merit to be used in the control logic, improving power efficiency, while still achieving the required high voltage control capability through the level shifter's voltage translation function
3Productivity
If low breakdown voltage transistors are used to control high voltage devices, then figure of merit is improved, but additional circuit complexity is introduced to handle voltage level differences
Solution Approach 1:
The level shifter with capacitive coupling provides a relatively simple intermediary structure that bridges the voltage gap between low voltage control signals and high voltage devices. This approach adds minimal circuit complexity compared to alternative solutions, while enabling the use of low voltage transistors with high figure of merit to achieve high operating frequencies
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 approach allows for the effective control of high voltage devices using low voltage transistors, improving performance and reducing costs by eliminating the need for expensive high voltage transistors, while maintaining reliability and efficiency in power management applications.
Implementation Method 1
The RC time constant of the RC circuit can be used to control a dead time between the falling edge of the LS output control signal and the rising edge of the HS output control signal
Implementation Method 2
employing capacitive coupling and clamping circuitry to generate control signals that can handle high voltages without imposing those voltages on the transistors
Data Source
AI summary
Systems, methods, and apparatus for use in biasing and driving high voltage semiconductor devices using only low voltage transistors are described. The apparatus and method are adapted to control multiple high voltage semiconductor devices to enable high voltage power control, such as power amplifiers, power management and conversion and other applications wherein a first voltage is large compared to the maximum voltage handling of the low voltage control transistors. Timing of control signals can be adjusted via internal and/or external components so as to minimize shoot trough currents in the high voltage devices. A DC/DC power conversion implementation from high input voltage to low output voltage using a novel level shifter which uses only low voltage transistors is also provided. Also presented is a level shifter in which floating nodes and high voltage capacitive coupling and control enable the high voltage control with low voltage transistors.