Power Transistor Chip With Built-In JFET Start-Up Circuit
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Solution Overview
Problem
Conventional AC/DC voltage converters require a separate start-up circuit that consumes unnecessary power and complicates the manufacturing process, increasing production costs.
Innovation Solution
A power transistor chip with a built-in junction field effect transistor acts as a start-up circuit, allowing for power conservation and simplifying the manufacturing process by eliminating the need for additional masks and processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate start-up circuit is used to initialize the pulse width modulation circuit, then the AC/DC voltage converter can be started up, but the start-up circuit consumes unnecessary power continuously and increases device complexity
Solution Approach 1:
The patent combines the start-up circuit function with the power transistor chip by integrating a junction field effect transistor (JFET) directly into the chip. The JFET is formed using the same manufacturing process as the power transistor, merging two previously separate functions (power switching and start-up) into a single integrated component. This eliminates the need for a separate start-up circuit and its associated continuous power consumption.
Solution Approach 2:
The built-in JFET start-up circuit is automatically controlled by the pulse width modulation circuit. When the PWM circuit outputs a high-level signal, the JFET turns off, causing the start-up circuit to automatically stop supplying power. This self-service mechanism eliminates unnecessary continuous power consumption while ensuring reliable start-up initialization.
2Use of energy by moving object
If depletion MOSFETs are integrated into the power transistor chip to create a start-up circuit, then power consumption is reduced, but the manufacturing process becomes more complicated with additional masks and processes
Solution Approach 1:
The patent changes the type of field effect transistor from depletion MOSFET to junction field effect transistor (JFET). This parameter change is crucial because JFETs can be manufactured using the same standard semiconductor fabrication process as power transistors, without requiring additional masks or special processes. The JFET structure uses doped regions that are naturally formed during the power transistor manufacturing process, making it compatible with existing production lines.
3Reliability
If depletion MOSFETs are integrated into the power transistor chip to create a start-up circuit, then the start-up function is achieved, but the device complexity increases due to additional channel requirements
Solution Approach 1:
The patent merges the start-up circuit function with the existing power transistor chip structure by integrating a JFET that shares the same substrate and manufacturing process. The JFET is formed using doped regions that are part of the standard power transistor fabrication sequence, eliminating the need for separate channels or additional structural elements that would increase device complexity.
Data Source
AI summary
A power transistor chip and an application circuit thereof have a junction field effect transistor to act as a start-up circuit of an AC/DC voltage converter. The start-up circuit can be turned off after the PWM circuit of the AC/DC voltage converter operates normally to conserve the consumption of the power. Besides, the junction field effect transistor is built in the power transistor chip. Because the junction field effect transistor is fabricated with the same manufacturing process as the power transistor, it is capable of simplifying the entire process and lowering the production cost due to no additional mask and manufacturing process.