Rectifier Device With Integrated MOS Transistor and Latch-Up Prevention
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Solution Overview
Problem
Conventional rectifier devices using silicon diodes experience significant power dissipation due to high forward voltage drop, which is a concern especially in low-voltage applications, and active rectification with power transistors requires complex control circuits to manage alternating supply voltages and prevent latch-up effects.
Innovation Solution
A rectifier device incorporating a power MOS transistor with an integrated diode and a control circuit that switches the MOS transistor on during diode forward bias, bypassing the diode with a low-resistive MOS channel, and includes a switching circuit to manage substrate voltage and prevent latch-up by connecting well regions to the anode terminal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If silicon diodes are used for rectification, then the device structure is simple, but power dissipation is high due to forward voltage drop of 0.6 to 0.7 volts
Solution Approach 1:
The patent changes the operating parameters of the MOS transistor by applying alternating supply voltages and using a control circuit to switch between different operating states (on-state during positive half-cycle, off-state during negative half-cycle), thereby achieving rectification with lower voltage drop compared to silicon diodes
Solution Approach 2:
The patent employs dynamic switching of the MOS transistor controlled by alternating supply voltages, where the transistor transitions between on and off states synchronously with the input voltage polarity, enabling adaptive rectification that reduces power dissipation while maintaining simple structure
2Loss of energy
If power MOS transistors are used for active rectification, then power dissipation is reduced, but device complexity increases due to required control circuits
Solution Approach 1:
The patent implements self-service control where the alternating supply voltages automatically control the MOS transistor switching without requiring external control circuits. The transistor turns on during positive half-cycles and off during negative half-cycles based on the inherent polarity of the supply voltage, eliminating the need for complex control logic
Solution Approach 2:
The patent extracts and eliminates the complex control circuit from the rectifier design by using the alternating supply voltages themselves to directly control the MOS transistor switching, thereby reducing device complexity while maintaining the low power dissipation benefits of active rectification
3Loss of energy
If power MOS transistors are used with alternating supply voltages, then power dissipation is reduced, but latch-up effects may occur
Solution Approach 1:
The patent applies preliminary anti-action by connecting the well regions to fixed potential terminals (anode terminal to positive supply, cathode terminal to negative supply) before the alternating voltage is applied, preventing latch-up effects from occurring in the first place by ensuring the pn-junctions remain properly biased throughout the voltage transitions
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
The solution significantly reduces power dissipation by minimizing the voltage drop across the rectifier device and prevents latch-up effects, allowing for efficient operation with low forward voltage behavior similar to a diode, while simplifying the control circuitry.
Implementation Method 1
The one or more well regions and the surrounding semiconductor body form a pn-junction
Implementation Method 2
power MOS field effect transistors (MOSFETs), which have a comparably low on-resistance and thus may produce a significantly lower voltage drop
Data Source
AI summary
A rectifier device is described herein. In accordance with one embodiment, the rectifier device includes a semiconductor body doped with dopants of a first doping type and one or more well regions arranged in the semiconductor body and doped with dopants of a second doping type. Thereby, the one or more well regions and the surrounding semiconductor body form a pn-junction. The rectifier device further includes an anode terminal and a cathode terminal connected by a load current path of a first MOS transistor and a diode, which is parallel to the load current path. An alternating input voltage is applied between the anode terminal and the cathode terminal during operation of the rectifier device. The rectifier device includes a control circuit that is configured to switch on the first MOS transistor for an on-time period, during which the diode is forward biased, wherein the first MOS transistor and the diode are integrated in the semiconductor body and the control circuit is at least partly arranged in the one or more well regions. Further, the rectifier device includes a switching circuit that is configured to electrically connect a first well region of the one or more well regions with the anode terminal, as long as the alternating input voltage is above a threshold value, and, to pull the voltage of first well region towards the alternating input voltage, as long as the alternating input voltage is at or below the threshold value.