Resonant Turn-Off Control for Low-Overvoltage Switching Elements
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In power electronics, high turn-off overvoltages occur during fast switching operations due to parasitic inductances in the current path, hindering loss-free or low-loss switching.
Innovation Solution
A control device adjusts the switching element's turn-off operation with a channel time duration shorter than the resonance vibration period, exciting a vibration in the commutation circuit, and determines the turn-off current based on the circuit's capacitances and inductances to satisfy specific conditions, allowing low-loss switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fast switching operations are performed in the range of 1 ns to 1000 ns, then switching speed is improved, but high turn-off overvoltages occur due to parasitic inductances
Solution Approach 1:
The patent applies resonant vibration of the commutation circuit to achieve zero overvoltage switching. By timing the switching operation to coincide with the natural resonance period of the circuit (determined by Lp and Ceff), the voltage oscillations are synchronized such that the switching occurs at the voltage minimum point, effectively eliminating turn-off overvoltages while maintaining fast switching speeds
Solution Approach 2:
The patent changes the switching timing parameter to match the resonance period of the commutation circuit. Specifically, the switching is performed when the current through the switching element satisfies the condition ITO,n = (VDC/π) × √(Ceff/Lp) × sin(π×toff/tres), where toff is the channel turn-off time and tres is the resonance period. This parameter adjustment allows fast switching without generating harmful overvoltages
2Productivity
If channel turn-off time duration is reduced to achieve faster switching, then productivity is improved, but turn-off overvoltages increase
Solution Approach 1:
The patent utilizes the periodic nature of the resonant oscillation in the commutation circuit. By synchronizing the switching operation with the periodic voltage waveform (specifically at the zero-crossing or minimum voltage point of the resonance cycle), the switching occurs at the optimal moment in each period, enabling fast switching without overvoltage generation
Solution Approach 2:
The patent employs a control device that monitors the current through the switching element and compares it against the calculated optimal current value (ITO,n). When the measured current satisfies the resonance condition within a tolerance range, the control device triggers the switching operation. This feedback mechanism ensures that switching occurs at the correct moment in the resonance cycle, maintaining both speed and low overvoltage
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 reduces turn-off overvoltages and enables efficient, low-loss switching operations in DC-DC converters and other power electronic circuits.
Implementation Method 1
the control device is configured to switch the switching element for the switching operation with a channel turn-off time duration that is shorter than a period duration of a resonance vibration of the commutation circuit, in order to excite a vibration in the commutation circuit
Data Source
AI summary
An apparatus includes a switch arrangement comprising a switching element and a control device that is configured to switch the switching element on the basis of a turn-off current that is determined by the relationship thatIT0,n=VDC(Ceff1+Ceff2)3Ceff1Ceff2Lpn πwherein IT0,n describes the turn-off current to be turned off by the switching element, VDC describes an intermediate circuit voltage of the commutation circuit, Ceff1 describes an effective capacitance of the commutation resonant circuit associated with the switching element, Ceff2 describes an effective capacitance of the commutation resonant circuit associated with the free-running element, Lp describes an effective electrical inductance of the commutation resonant circuit, and n describes a natural number; wherein at least one of the conditions is satisfied:n=2i+1,i∈;1)Ceff1≠Ceff2 for n=2i+1,i∈.2)