Rectifier Clamping Voltage Control for MOSFET Thermal Overload
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Active rectifiers with MOSFET transistors face uneven current distribution and thermal overloading during load shedding due to the negative temperature coefficient of the threshold voltage, leading to positive feedback effects and inefficient power loss distribution.
Innovation Solution
A method that dynamically controls the clamping voltage to compensate for the negative temperature coefficient by implementing a time-controlled increase in clamping voltage within each half-sine wave of the load shedding event, and integrating a zener diode directly with the MOSFET transistor for thermal coupling, ensuring equal power loss distribution across switching branches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If MOSFET transistors are used as power switches in active rectifiers, then power loss is significantly reduced compared to diode rectifiers, but uneven current distribution and thermal overloading occur during load shedding due to the negative temperature coefficient of the threshold voltage
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the clamping voltage parameter during load shedding events. The control unit increases the clamping voltage from an initial value to a higher value within a defined time window, which compensates for the negative temperature coefficient effect of MOSFET threshold voltage. This dynamic parameter adjustment ensures uniform current distribution across parallel switching branches while maintaining the low power loss benefits of active MOSFET switches.
2Reliability
If the clamping voltage is made up of the breakdown voltage of a zener diode and the threshold voltage of the MOSFET transistor, then voltage clamping is achieved, but the positive temperature coefficient of the zener diode cannot compensate for the negative temperature coefficient of the MOSFET threshold voltage due to insufficient thermal coupling
Solution Approach 1:
The patent introduces a control unit as an intermediary that actively manages the clamping voltage during load shedding events. Instead of relying solely on passive thermal coupling between the zener diode and MOSFET, the control unit dynamically adjusts the clamping voltage based on predefined criteria, effectively mediating the temperature compensation function and ensuring uniform current distribution across switching branches.
3Temperature
If the threshold voltage of MOSFET transistors decreases with increasing temperature, then the clamping voltage decreases, but this causes unequal distribution of current and temperature, increasing the unequal distribution of current through positive feedback
Solution Approach 1:
The patent applies preliminary anti-action by preemptively increasing the clamping voltage at the onset of load shedding events, before thermal runaway can occur. The control unit detects the load shedding condition and immediately adjusts the clamping voltage within a defined time window, counteracting the negative temperature coefficient effect before it can cause uneven current distribution and positive feedback thermal runout.
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 approach achieves a nearly uniform distribution of power loss across MOSFET transistors, preventing thermal overloading and maintaining voltage supply during load shedding, while avoiding complex thermal coupling technologies and avalanche operations.
Implementation Method 1
integrating a zener diode directly with the MOSFET transistor for thermal coupling
Implementation Method 2
compensate for the negative temperature coefficient of the threshold voltage
Implementation Method 3
avoiding complex thermal coupling technologies and avalanche operations
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a method for controlling a rectifier comprising active switching elements (40, 42, 50, 52, 60, 62) in the event of a drop in load, wherein the active switching elements (40, 42, 50, 52, 60, 62) are controlled during the voltage clamping such that the clamping voltage behaves according to a predetermined time-dependent signal form in at least one switching branch (30, 32, 34) within at least a half-cycle of the current to be rectified.