Rectifier Device Clamping Circuit Low Voltage Drop
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Solution Overview
Problem
Conventional rectifier devices using silicon diodes experience significant power dissipation due to their forward voltage drop, which is a substantial portion of the total power consumption, especially in applications requiring low voltage conversion, and require complex control circuits when using active rectification with power transistors.
Innovation Solution
A rectifier device comprising a power MOSFET with an intrinsic diode in parallel, where the MOSFET is switched on to bypass the diode when forward biased, and a clamping circuit adjusts the voltage drop based on load current, reducing power dissipation and eliminating the need for complex control circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If silicon diodes are used in rectifier devices, then the rectifier structure is simple, but power dissipation is significant due to forward voltage drop of 0.6 to 0.7 volts
Solution Approach 1:
The patent changes the operating parameters of the MOSFET by dynamically adjusting the gate-source voltage to keep the device in the saturation region during conduction. This parameter control enables the MOSFET to operate with very low voltage drop (100-200 millivolts) while maintaining adequate current flow, thereby significantly reducing power dissipation compared to silicon diodes
2Loss of energy
If active rectification with power transistors is used, then power dissipation is reduced, but a complex control circuit is required to switch the transistor synchronously
Solution Approach 1:
The patent implements self-service by using the rectifier device's own output voltage to drive the gate of the MOSFET. The cathode voltage directly controls the gate-source voltage, creating a self-regulating system that automatically adjusts the MOSFET conduction without requiring external control circuits or synchronous switching signals
Solution Approach 2:
The MOSFET's intrinsic body diode serves multiple functions: it provides the clamping path during reverse bias conditions and works in conjunction with the MOSFET channel during forward conduction. This multi-functionality eliminates the need for separate clamping components and simplifies the overall circuit structure
3Reliability
If a clamping circuit is added to protect against overvoltage, then load protection is improved, but device complexity increases
Solution Approach 1:
The MOSFET's intrinsic body diode serves as an integrated clamping element that works in conjunction with the MOSFET channel. During reverse bias conditions, the body diode provides the clamping path, eliminating the need for separate Zener diodes or voltage regulator circuits while maintaining overvoltage protection functionality
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 forward voltage drop to approximately 100-200 millivolts, enhancing efficiency and simplifying control logic, while providing clamping functionality to protect against overvoltage.
Implementation Method 1
power transistors such as power MOS field effect transistors (MOSFETs) or power bipolar junction transistors (BJTs), which have a comparably low on-resistance and thus may produce a significantly lower voltage drop
Implementation Method 2
the rectifier should have a clamping functionality (e.g. like a Zener diode) to avoid an overvoltage between the battery terminals
Data Source
AI summary
A rectifier device includes a first transistor having a load current path and a diode connected in parallel to the load current path between an anode terminal and a cathode terminal. An alternating input voltage is operably applied between the anode terminal and the cathode terminal. A control circuit is coupled to a gate terminal of the first transistor and configured to switch the first transistor on for an on-time period, during which the diode is forward biased. A clamping circuit is coupled to the gate terminal of the first transistor and configured to at least partly switch on the first transistor while the diode is reverse biased and when the level of the alternating input voltage reaches a clamping voltage. The clamping circuit includes an additional circuit coupled between the cathode terminal and the gate terminal and configured to provide a voltage dependent on a load current.