Stacked Power Stage Using Low-Voltage FETs for 40V Breakdown
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Solution Overview
Problem
High-voltage power transistors require more area and consume more power than low-voltage transistors, and their gate drive circuits are larger and more power-hungry, posing challenges in applications like automotive battery switching regulators that need to withstand voltages up to 40V or more without sustaining damage.
Innovation Solution
A power circuit design using a combination of high-voltage and low-voltage rated transistors in a stacked configuration, with a bleeder circuit to prevent voltage across the transistors from exceeding breakdown voltage, and an integrated circuit structure with a floating voltage diffusion layer to manage voltage and reduce power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-voltage rated transistors are used to withstand 40V or more, then the breakdown voltage capability is improved, but the transistor area and power consumption increase significantly
Solution Approach 1:
The patent divides a single high-voltage transistor into multiple stacked transistors with different voltage ratings (e.g., 30V and 5V transistors in series). This segmentation allows each transistor to operate within its optimal voltage range, achieving the required 40V+ breakdown capability while using smaller, more efficient low-voltage transistor structures that consume less area and power.
2Reliability
If high-voltage rated transistors are used to withstand 40V or more, then the breakdown voltage capability is improved, but the power consumption increases
Solution Approach 1:
By segmenting the high-voltage function into stacked transistors with different voltage ratings, the patent enables each transistor to operate at its optimal efficiency point. Low-voltage transistors consume less power than their high-voltage counterparts, so the stacked configuration reduces overall power consumption while maintaining the required 40V+ breakdown voltage capability.
3Reliability
If high-voltage rated transistors are used, then the breakdown voltage capability is improved, but the gate drive circuit area and power consumption increase
Solution Approach 1:
The gate drive circuit is segmented into multiple independent drive circuits, one for each stacked transistor. Each gate drive circuit is simpler and smaller than a single high-voltage gate drive, reducing overall gate drive circuit area and power consumption while maintaining the ability to control the stacked transistor configuration for 40V+ breakdown voltage capability.
Data Source
AI summary
Described embodiments include a voltage converter power circuit having a high-voltage rated first transistor with a first current terminal coupled to an input voltage terminal, and a second current terminal. A second transistor, a low-voltage rated transistor, has a second control terminal, a third current terminal coupled to the second current terminal, and a fourth current terminal coupled to a switching terminal. A third transistor, a high-voltage rated transistor, has a fifth current terminal coupled to the switching terminal, a sixth current terminal, and a third control terminal. A fourth transistor, a low-voltage rated transistor, is coupled between the sixth current terminal and a ground terminal. A bleeder circuit is coupled between the seventh and eighth current terminals and is configured to prevent a voltage across the fourth transistor from exceeding a breakdown voltage.