Power Conversion Circuit With Clamping Diode For dV/dt Reduction
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Solution Overview
Problem
Power conversion circuits face limitations in reducing the rate of change of voltage (dV/dt) without significantly increasing switching losses, particularly when using switching devices that cannot effectively decrease dV/dt by increasing gate resistance, leading to excessive voltage surges and increased switching losses.
Innovation Solution
A power conversion circuit is designed with a clamping diode and inductors between switching devices and an inductive load, allowing for a current resonance type soft switching operation, which reduces dV/dt and switching losses by delaying the onset of high current flow and using capacitors in parallel with switching devices to maintain low turn-off losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If gate resistance is increased to decrease dV/dt, then voltage surge is reduced, but switching losses increase significantly
Solution Approach 1:
A clamping diode is introduced as an intermediary component connected in parallel with the switching device. The diode clamps the voltage across the switching device during turn-off, limiting the voltage surge without requiring increased gate resistance. This mediator allows the switching device to maintain high-speed switching characteristics while the diode handles the voltage limiting function, thereby reducing switching losses compared to conventional gate resistance methods.
Solution Approach 2:
The invention changes the operational parameters of the switching device by controlling the gate voltage waveform and introducing a clamping voltage level. By adjusting the gate resistance to an optimal value (not excessively high) and setting a specific clamping voltage threshold, the system achieves reduced dV/dt and voltage surge while maintaining low switching losses. This parameter optimization resolves the contradiction between voltage surge reduction and switching loss minimization.
2Productivity
If switching speed is increased to improve productivity, then power conversion efficiency improves, but voltage surge and switching losses increase
Solution Approach 1:
The clamping diode acts as a mediator that enables high-speed switching by handling the voltage surge protection function. This allows the switching device to operate at high speeds for improved productivity while the diode clamps excessive voltage, preventing the typical increase in switching losses that would accompany high-speed operation. The intermediary component decouples the relationship between switching speed and voltage surge.
Solution Approach 2:
The invention converts the potentially harmful effect of high dV/dt during fast switching into a beneficial outcome. By allowing fast switching to occur and then clamping the resulting voltage surge with the diode, the system transforms what would be a harmful voltage spike into a controlled phenomenon. This enables high-speed switching for improved productivity while the clamped voltage surge is dissipated in a controlled manner, preventing excessive switching losses.
3Object-affected harmful factors
If dV/dt is reduced to decrease voltage surge, then voltage surge is reduced, but switching losses increase due to extended switching time
Solution Approach 1:
The clamping diode serves as an intermediary that reduces voltage surge without requiring extended switching time. By providing an alternative current path through the diode during turn-off, the voltage across the switching device is clamped, achieving voltage surge reduction while the switching device maintains its fast switching characteristics. This eliminates the need to extend switching time, thereby avoiding increased switching losses.
Solution Approach 2:
The invention segments the voltage surge protection function from the switching operation itself. Instead of using a single mechanism that both slows switching and reduces voltage surge (like high gate resistance), the system separates these functions: the switching device handles fast switching while the clamping diode handles voltage surge reduction independently. This segmentation allows both fast switching and voltage surge reduction without the trade-off present in conventional approaches.
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 circuit effectively decreases dV/dt without increasing switching losses, achieving reduced turn-off and turn-on losses, and maintaining low turn-off losses even when reducing dV/dt, making it suitable for high-speed switching applications.
Implementation Method 1
allowing for a current resonance type soft switching operation, which reduces dV/dt and switching losses
Implementation Method 2
using capacitors in parallel with switching devices to maintain low turn-off losses
Implementation Method 3
delaying the onset of high current flow
Data Source
AI summary
A power conversion circuit converting DC electric power into AC electric power and sending the AC power to an inductive load, includes a first switching device connected to the DC power supply; a second switching device connected to the DC power supply; a first inductor provided between the first switching device and the inductive load; a second inductor provided between the second switching device and the inductive load; and a clamping diode connected between a first connection point between the first switching device and the first inductor, and a second connection point between the second switching device and the second inductor. When the first and second switching devices are turned off, a current flows through the second diode, clamping diode, first inductor and inductive load to completely flow out a current in the first inductor, and then a current flows through the second diode, second inductor and inductive load.