Lateral Power MOSFET Switching Transistor for AC/DC Converter
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Solution Overview
Problem
Conventional switching power source systems face challenges with increased chip size, cost, and efficiency due to high gate capacitance in vertical power MOSFETs, long wiring causing signal distortion, and heat dissipation issues, leading to inefficient power conversion and increased power consumption.
Innovation Solution
The use of a lateral power MOSFET as a switching transistor with a control IC, where the switching transistor and control IC are separate chips in a single package, with optimized layout and insulation to reduce noise and heat transfer, and employing a slit between the chips for heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a vertical power MOSFET is used as a switching transistor, then the device can be packaged in a compact form, but the gate capacitance increases due to the parasitic J-FET between adjacent bodies, leading to increased chip size and cost
Solution Approach 1:
The patent segments the package into two separate chips: a control IC chip containing the control circuit and a switching transistor chip containing the vertical power MOSFET. This segmentation allows each chip to be optimized independently, enabling the use of a vertical power MOSFET with compact packaging while managing gate capacitance through separate chip design and reduced wiring length.
2Quantity of substance
If the control IC and switching transistor are separately packaged, then the gate capacitance can be reduced, but the wiring length increases causing signal distortion and requiring additional insulation measures
Solution Approach 1:
The patent merges the control IC and switching transistor into a single package housing, placing them in close proximity. This combining approach reduces the wiring length between the control circuit and switching transistor, minimizing signal distortion while maintaining the benefits of separate chip design for managing gate capacitance.
3Length of stationary object
If the control IC and switching transistor are placed close together in one package, then the wiring length is reduced, but heat dissipation becomes problematic due to the high power consumption of the switching transistor
Solution Approach 1:
The patent applies local quality by providing a dedicated heat dissipation structure specifically for the switching transistor chip, while the control IC chip has its own separate heat dissipation path. This localized heat management allows the components to be placed close together for reduced wiring length while effectively managing the thermal characteristics of each component.
4Reliability
If insulation measures are added between the control IC and switching transistor, then the electrical isolation is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the insulation requirement by providing an insulating film specifically at the die bonding area where the switching transistor chip is mounted. This targeted insulation approach electrical isolates the control IC from the high-voltage switching transistor only where necessary, rather than implementing complex insulation throughout the entire package, thus reducing device complexity and manufacturing cost.
Data Source
AI summary
In one embodiment of the present invention, an output control device is disclosed capable of reducing a chip size and realizing a low cost. An output control device includes a switching transistor controlling an output voltage by having an on/off time ratio controlled and a control IC controlling the on/off time ratio of the switching transistor on the basis of the output voltage controlled by the switching transistor. The switching transistor is made of a lateral power MOSFET.