Rectifier Circuit Arrangement with Cascade MOSFETs
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Solution Overview
Problem
Conventional rectifiers, such as diodes and power MOSFETs, experience significant losses and switching delays due to reverse recovery effects and output capacitance, which are particularly problematic in high-power conversion applications.
Innovation Solution
A rectifier circuit arrangement featuring a cascade-like configuration of MOSFETs with a series connection of second semiconductor devices, where each device's control terminal is connected to either a load terminal of another device, allowing for reduced switching losses and faster switching times by bypassing the body diode during forward conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a diode is used as a rectifier, then the rectifier structure is simple, but significant conduction losses occur that are proportional to the current
Solution Approach 1:
The patent changes the operating parameters of the MOSFET by controlling the gate-source voltage to operate in different regions (linear region for forward conduction, saturation region for reverse blocking), thereby achieving low conduction losses while maintaining rectifier functionality with a simple structure
2Loss of energy
If a power MOSFET is used as a rectifier, then conduction losses are reduced, but switching delays occur due to significant output capacitance
Solution Approach 1:
The body diode is utilized to perform preliminary conduction during the reverse bias state, which prepares the circuit state before the MOSFET switching event. This preliminary action through the body diode reduces the charging current required during MOSFET turn-on, thereby reducing both switching losses and switching delays
3Reliability
If a conventional MOSFET with body diode is used, then reverse blocking is achieved, but the body diode causes reverse recovery effects that increase losses
Solution Approach 1:
The patent extracts or bypasses the harmful reverse recovery effect by using the body diode only for its useful function of pre-charging the output capacitance during reverse bias, while preventing it from causing reverse recovery losses during forward conduction. The control circuit ensures the MOSFET is properly switched to avoid the reverse recovery problem
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 configuration significantly reduces switching losses and enhances switching speed by minimizing the impact of output capacitance and reverse recovery effects, leading to more efficient power conversion with lower voltage blocking capabilities.
Implementation Method 1
Rectifiers are electronic circuits or electronic devices that allow a current to flow in a first direction, while preventing a current to flow in an opposite second direction
Implementation Method 2
A diode that conducts a current when forward biased and that blocks when reverse biased
Implementation Method 3
A diode that conducts a current when forward biased and that blocks when reverse biased
Implementation Method 4
power MOSFETs, that may be used in rectifiers, in drive applications or an power conversion applications, may have a significant output capacitance that needs to be charged/discharged each time the MOSFET is switched on/off
Data Source
AI summary
A rectifier circuit includes first and second load terminals, a first semiconductor device having a load path and configured to receive a drive signal, and a plurality of second semiconductor devices each having a load path and each configured to receive a drive signal. The load paths of the second semiconductor devices are connected in series, and connected in series to the load path of the first semiconductor device. A series circuit with the first semiconductor device and the second semiconductor devices is connected between the load terminals. Each of the second semiconductor devices is configured to receive as a drive voltage either a load-path voltage of at least one of the second semiconductor devices, or a load-path of at least the first semiconductor device. The first semiconductor device is configured to receive as a drive voltage a load-path-voltage of at least one of the second semiconductor devices.