VDMOS Power Path Switching Without Current-Sense Resistors
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Solution Overview
Problem
Conventional flyback power supply circuits require a highly accurate resistor for current detection, increasing cost and layout area on printed circuit boards (PCBs), as they need space for accommodating the resistor and a transistor to switch current effectively.
Innovation Solution
A power path switch circuit utilizing a power transistor unit with VDMOS devices and a voltage locking circuit, integrated into a multi-chip module, which controls the power path conduction and locks voltage ratios between conductive currents through VDMOS devices, eliminating the need for a resistor and transistor, thereby reducing PCB layout area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a highly accurate resistor is used to detect secondary side current, then measurement precision is improved, but cost increases and layout area increases
Solution Approach 1:
The patent merges the current detection function and power switching function into a single integrated circuit. The first VDMOS device serves both as a power switch and a current sensing element, eliminating the need for separate resistors and transistors. This integration reduces PCB layout area while maintaining measurement precision through the integrated circuit's internal design.
Solution Approach 2:
The first VDMOS device performs multiple functions: it acts as a power switch controlled by the control signal and simultaneously serves as a current sensing element whose conductive current provides feedback for voltage locking. This multi-functionality eliminates the need for separate dedicated current detection components, reducing overall layout area.
2Reliability
If separate resistor and transistor are used for current detection and switching, then device reliability is improved through functional separation, but device complexity increases
Solution Approach 1:
The patent combines multiple discrete components (resistor for current detection, transistor for switching) into an integrated circuit containing VDMOS devices. The first VDMOS device integrates power switching and current sensing capabilities, while the second VDMOS device handles voltage locking control. This integration reduces component count and circuit complexity while maintaining reliability through coordinated operation of the integrated devices.
Solution Approach 2:
The patent implements a feedback mechanism where the conductive current of the first VDMOS device is sensed and used by the voltage locking circuit to control the second VDMOS device. This feedback loop ensures reliable current control by automatically adjusting the power path based on actual current conditions, maintaining system reliability despite integration.
3Ease of manufacture
If conventional discrete components are used, then ease of manufacture is improved through modular assembly, but productivity decreases due to larger layout area
Solution Approach 1:
The patent integrates multiple discrete components into a single integrated circuit module containing VDMOS devices. This integration dramatically reduces the PCB layout area required, allowing for more compact power supply designs and higher manufacturing density. The integrated circuit can be manufactured using standard semiconductor fabrication processes, improving overall manufacturing efficiency despite the increased complexity of the integrated structure.
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 solution effectively reduces the layout area of printed circuit boards by omitting the resistor and transistor, saving manufacturing costs and allowing for more compact transformer designs.
Implementation Method 1
the voltage locking circuit is configured to operably lock a voltage at the second current outflow end at a voltage at the first current outflow end, so that there is a predetermined ratio between a first conductive current flowing through the first VDMOS device and a second conductive current flowing through the second VDMOS device
Implementation Method 2
an error amplifier having a non-inverting input end and an inverting input end, which are coupled to the first current outflow end and the second current outflow end, respectively
Data Source
AI summary
A power path switch circuit includes: a power transistor unit including: a first vertical double-diffused metal oxide semiconductor (VDMOS) device, wherein a first current outflow end of the first VDMOS device is coupled to an output end of a power path; and a second VDMOS device, wherein a first current inflow end of the first VDMOS device and a second current inflow end of the second VDMOS device are coupled with a supply end of the power path; and a voltage locking circuit coupled to the first current outflow end and the second current outflow end, for locking a voltage at the second current outflow end to a voltage at the first current outflow end, so that there is a predetermined ratio between a first conductive current flowing through the first VDMOS device and a second conductive current flowing through the second VDMOS device.